I have installed the disco-proposed 'procps' package and was able to conclude that it fixes the situation based on the reproducer suggested upstream:
$ vi $(seq 1 1250| paste -s -d'_')_foo.txt # Creating a process containing > 4096 chars, to be precise 5158 chars)
$ pgrep -af 'foo.txt'
1148 vi 1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40_41_42_43_44_45_46_47_48_49_50_51_52_53_54_55_56_57_58_59_60_61_62_63_64_65_66_67_68_69_70_71_72_73_74_75_76_77_78_79_80_81_82_83_84_85_86_87_88_89_90_91_92_93_94_95_96_97_98_99_100_101_102_103_104_105_106_107_108_109_110_111_112_113_114_115_116_117_118_119_120_121_122_123_124_125_126_127_128_129_130_131_132_133_134_135_136_137_138_139_140_141_142_143_144_145_146_147_148_149_150_151_152_153_154_155_156_157_158_159_160_161_162_163_164_165_166_167_168_169_170_171_172_173_174_175_176_177_178_179_180_181_182_183_184_185_186_187_188_189_190_191_192_193_194_195_196_197_198_199_200_201_202_203_204_205_206_207_208_209_210_211_212_213_214_215_216_217_218_219_220_221_222_223_224_225_226_227_228_229_230_231_232_233_234_235_236_237_238_239_240_241_242_243_244_245_246_247_248_249_250_251_252_253_254_255_256_257_258_259_260_261_262_263_264_265_266_267_268_269_270_271_272_273_274_275_276_277_278_279_280_281_282_283_284_285_286_287_288_289_290_291_292_293_294_295_296_297_298_299_300_301_302_303_304_305_306_307_308_309_310_311_312_313_314_315_316_317_318_319_320_321_322_323_324_325_326_327_328_329_330_331_332_333_334_335_336_337_338_339_340_341_342_343_344_345_346_347_348_349_350_351_352_353_354_355_356_357_358_359_360_361_362_363_364_365_366_367_368_369_370_371_372_373_374_375_376_377_378_379_380_381_382_383_384_385_386_387_388_389_390_391_392_393_394_395_396_397_398_399_400_401_402_403_404_405_406_407_408_409_410_411_412_413_414_415_416_417_418_419_420_421_422_423_424_425_426_427_428_429_430_431_432_433_434_435_436_437_438_439_440_441_442_443_444_445_446_447_448_449_450_451_452_453_454_455_456_457_458_459_460_461_462_463_464_465_466_467_468_469_470_471_472_473_474_475_476_477_478_479_480_481_482_483_484_485_486_487_488_489_490_491_492_493_494_495_496_497_498_499_500_501_502_503_504_505_506_507_508_509_510_511_512_513_514_515_516_517_518_519_520_521_522_523_524_525_526_527_528_529_530_531_532_533_534_535_536_537_538_539_540_541_542_543_544_545_546_547_548_549_550_551_552_553_554_555_556_557_558_559_560_561_562_563_564_565_566_567_568_569_570_571_572_573_574_575_576_577_578_579_580_581_582_583_584_585_586_587_588_589_590_591_592_593_594_595_596_597_598_599_600_601_602_603_604_605_606_607_608_609_610_611_612_613_614_615_616_617_618_619_620_621_622_623_624_625_626_627_628_629_630_631_632_633_634_635_636_637_638_639_640_641_642_643_644_645_646_647_648_649_650_651_652_653_654_655_656_657_658_659_660_661_662_663_664_665_666_667_668_669_670_671_672_673_674_675_676_677_678_679_680_681_682_683_684_685_686_687_688_689_690_691_692_693_694_695_696_697_698_699_700_701_702_703_704_705_706_707_708_709_710_711_712_713_714_715_716_717_718_719_720_721_722_723_724_725_726_727_728_729_730_731_732_733_734_735_736_737_738_739_740_741_742_743_744_745_746_747_748_749_750_751_752_753_754_755_756_757_758_759_760_761_762_763_764_765_766_767_768_769_770_771_772_773_774_775_776_777_778_779_780_781_782_783_784_785_786_787_788_789_790_791_792_793_794_795_796_797_798_799_800_801_802_803_804_805_806_807_808_809_810_811_812_813_814_815_816_817_818_819_820_821_822_823_824_825_826_827_828_829_830_831_832_833_834_835_836_837_838_839_840_841_842_843_844_845_846_847_848_849_850_851_852_853_854_855_856_857_858_859_860_861_862_863_864_865_866_867_868_869_870_871_872_873_874_875_876_877_878_879_880_881_882_883_884_885_886_887_888_889_890_891_892_893_894_895_896_897_898_899_900_901_902_903_904_905_906_907_908_909_910_911_912_913_914_915_916_917_918_919_920_921_922_923_924_925_926_927_928_929_930_931_932_933_934_935_936_937_938_939_940_941_942_943_944_945_946_947_948_949_950_951_952_953_954_955_956_957_958_959_960_961_962_963_964_965_966_967_968_969_970_971_972_973_974_975_976_977_978_979_980_981_982_983_984_985_986_987_988_989_990_991_992_993_994_995_996_997_998_999_1000_1001_1002_1003_1004_1005_1006_1007_1008_1009_1010_1011_1012_1013_1014_1015_1016_1017_1018_1019_1020_1021_1022_1023_1024_1025_1026_1027_1028_1029_1030_1031_1032_1033_1034_1035_1036_1037_1038_1039_1040_1041_1042_1043_1044_1045_1046_1047_1048_1049_1050_1051_1052_1053_1054_1055_1056_1057_1058_1059_1060_1061_1062_1063_1064_1065_1066_1067_1068_1069_1070_1071_1072_1073_1074_1075_1076_1077_1078_1079_1080_1081_1082_1083_1084_1085_1086_1087_1088_1089_1090_1091_1092_1093_1094_1095_1096_1097_1098_1099_1100_1101_1102_1103_1104_1105_1106_1107_1108_1109_1110_1111_1112_1113_1114_1115_1116_1117_1118_1119_1120_1121_1122_1123_1124_1125_1126_1127_1128_1129_1130_1131_1132_1133_1134_1135_1136_1137_1138_1139_1140_1141_1142_1143_1144_1145_1146_1147_1148_1149_1150_1151_1152_1153_1154_1155_1156_1157_1158_1159_1160_1161_1162_1163_1164_1165_1166_1167_1168_1169_1170_1171_1172_1173_1174_1175_1176_1177_1178_1179_1180_1181_1182_1183_1184_1185_1186_1187_1188_1189_1190_1191_1192_1193_1194_1195_1196_1197_1198_1199_1200_1201_1202_1203_1204_1205_1206_1207_1208_1209_1210_1211_1212_1213_1214_1215_1216_1217_1218_1219_1220_1221_1222_1223_1224_1225_1226_1227_1228_1229_1230_1231_1232_1233_1234_1235_1236_1237_1238_1239_1240_1241_1242_1243_1244_1245_1246_1247_1248_1249_1250_foo.txt
[VERIFICATION DISCO]
I have installed the disco-proposed 'procps' package and was able to conclude that it fixes the situation based on the reproducer suggested upstream:
$ vi $(seq 1 1250| paste -s -d'_')_foo.txt # Creating a process containing > 4096 chars, to be precise 5158 chars) 5_6_7_8_ 9_10_11_ 12_13_14_ 15_16_17_ 18_19_20_ 21_22_23_ 24_25_26_ 27_28_29_ 30_31_32_ 33_34_35_ 36_37_38_ 39_40_41_ 42_43_44_ 45_46_47_ 48_49_50_ 51_52_53_ 54_55_56_ 57_58_59_ 60_61_62_ 63_64_65_ 66_67_68_ 69_70_71_ 72_73_74_ 75_76_77_ 78_79_80_ 81_82_83_ 84_85_86_ 87_88_89_ 90_91_92_ 93_94_95_ 96_97_98_ 99_100_ 101_102_ 103_104_ 105_106_ 107_108_ 109_110_ 111_112_ 113_114_ 115_116_ 117_118_ 119_120_ 121_122_ 123_124_ 125_126_ 127_128_ 129_130_ 131_132_ 133_134_ 135_136_ 137_138_ 139_140_ 141_142_ 143_144_ 145_146_ 147_148_ 149_150_ 151_152_ 153_154_ 155_156_ 157_158_ 159_160_ 161_162_ 163_164_ 165_166_ 167_168_ 169_170_ 171_172_ 173_174_ 175_176_ 177_178_ 179_180_ 181_182_ 183_184_ 185_186_ 187_188_ 189_190_ 191_192_ 193_194_ 195_196_ 197_198_ 199_200_ 201_202_ 203_204_ 205_206_ 207_208_ 209_210_ 211_212_ 213_214_ 215_216_ 217_218_ 219_220_ 221_222_ 223_224_ 225_226_ 227_228_ 229_230_ 231_232_ 233_234_ 235_236_ 237_238_ 239_240_ 241_242_ 243_244_ 245_246_ 247_248_ 249_250_ 251_252_ 253_254_ 255_256_ 257_258_ 259_260_ 261_262_ 263_264_ 265_266_ 267_268_ 269_270_ 271_272_ 273_274_ 275_276_ 277_278_ 279_280_ 281_282_ 283_284_ 285_286_ 287_288_ 289_290_ 291_292_ 293_294_ 295_296_ 297_298_ 299_300_ 301_302_ 303_304_ 305_306_ 307_308_ 309_310_ 311_312_ 313_314_ 315_316_ 317_318_ 319_320_ 321_322_ 323_324_ 325_326_ 327_328_ 329_330_ 331_332_ 333_334_ 335_336_ 337_338_ 339_340_ 341_342_ 343_344_ 345_346_ 347_348_ 349_350_ 351_352_ 353_354_ 355_356_ 357_358_ 359_360_ 361_362_ 363_364_ 365_366_ 367_368_ 369_370_ 371_372_ 373_374_ 375_376_ 377_378_ 379_380_ 381_382_ 383_384_ 385_386_ 387_388_ 389_390_ 391_392_ 393_394_ 395_396_ 397_398_ 399_400_ 401_402_ 403_404_ 405_406_ 407_408_ 409_410_ 411_412_ 413_414_ 415_416_ 417_418_ 419_420_ 421_422_ 423_424_ 425_426_ 427_428_ 429_430_ 431_432_ 433_434_ 435_436_ 437_438_ 439_440_ 441_442_ 443_444_ 445_446_ 447_448_ 449_450_ 451_452_ 453_454_ 455_456_ 457_458_ 459_460_ 461_462_ 463_464_ 465_466_ 467_468_ 469_470_ 471_472_ 473_474_ 475_476_ 477_478_ 479_480_ 481_482_ 483_484_ 485_486_ 487_488_ 489_490_ 491_492_ 493_494_ 495_496_ 497_498_ 499_500_ 501_502_ 503_504_ 505_506_ 507_508_ 509_510_ 511_512_ 513_514_ 515_516_ 517_518_ 519_520_ 521_522_ 523_524_ 525_526_ 527_528_ 529_530_ 531_532_ 533_534_ 535_536_ 537_538_ 539_540_ 541_542_ 543_544_ 545_546_ 547_548_ 549_550_ 551_552_ 553_554_ 555_556_ 557_558_ 559_560_ 561_562_ 563_564_ 565_566_ 567_568_ 569_570_ 571_572_ 573_574_ 575_576_ 577_578_ 579_580_ 581_582_ 583_584_ 585_586_ 587_588_ 589_590_ 591_592_ 593_594_ 595_596_ 597_598_ 599_600_ 601_602_ 603_604_ 605_606_ 607_608_ 609_610_ 611_612_ 613_614_ 615_616_ 617_618_ 619_620_ 621_622_ 623_624_ 625_626_ 627_628_ 629_630_ 631_632_ 633_634_ 635_636_ 637_638_ 639_640_ 641_642_ 643_644_ 645_646_ 647_648_ 649_650_ 651_652_ 653_654_ 655_656_ 657_658_ 659_660_ 661_662_ 663_664_ 665_666_ 667_668_ 669_670_ 671_672_ 673_674_ 675_676_ 677_678_ 679_680_ 681_682_ 683_684_ 685_686_ 687_688_ 689_690_ 691_692_ 693_694_ 695_696_ 697_698_ 699_700_ 701_702_ 703_704_ 705_706_ 707_708_ 709_710_ 711_712_ 713_714_ 715_716_ 717_718_ 719_720_ 721_722_ 723_724_ 725_726_ 727_728_ 729_730_ 731_732_ 733_734_ 735_736_ 737_738_ 739_740_ 741_742_ 743_744_ 745_746_ 747_748_ 749_750_ 751_752_ 753_754_ 755_756_ 757_758_ 759_760_ 761_762_ 763_764_ 765_766_ 767_768_ 769_770_ 771_772_ 773_774_ 775_776_ 777_778_ 779_780_ 781_782_ 783_784_ 785_786_ 787_788_ 789_790_ 791_792_ 793_794_ 795_796_ 797_798_ 799_800_ 801_802_ 803_804_ 805_806_ 807_808_ 809_810_ 811_812_ 813_814_ 815_816_ 817_818_ 819_820_ 821_822_ 823_824_ 825_826_ 827_828_ 829_830_ 831_832_ 833_834_ 835_836_ 837_838_ 839_840_ 841_842_ 843_844_ 845_846_ 847_848_ 849_850_ 851_852_ 853_854_ 855_856_ 857_858_ 859_860_ 861_862_ 863_864_ 865_866_ 867_868_ 869_870_ 871_872_ 873_874_ 875_876_ 877_878_ 879_880_ 881_882_ 883_884_ 885_886_ 887_888_ 889_890_ 891_892_ 893_894_ 895_896_ 897_898_ 899_900_ 901_902_ 903_904_ 905_906_ 907_908_ 909_910_ 911_912_ 913_914_ 915_916_ 917_918_ 919_920_ 921_922_ 923_924_ 925_926_ 927_928_ 929_930_ 931_932_ 933_934_ 935_936_ 937_938_ 939_940_ 941_942_ 943_944_ 945_946_ 947_948_ 949_950_ 951_952_ 953_954_ 955_956_ 957_958_ 959_960_ 961_962_ 963_964_ 965_966_ 967_968_ 969_970_ 971_972_ 973_974_ 975_976_ 977_978_ 979_980_ 981_982_ 983_984_ 985_986_ 987_988_ 989_990_ 991_992_ 993_994_ 995_996_ 997_998_ 999_1000_ 1001_1002_ 1003_1004_ 1005_1006_ 1007_1008_ 1009_1010_ 1011_1012_ 1013_1014_ 1015_1016_ 1017_1018_ 1019_1020_ 1021_1022_ 1023_1024_ 1025_1026_ 1027_1028_ 1029_1030_ 1031_1032_ 1033_1034_ 1035_1036_ 1037_1038_ 1039_1040_ 1041_1042_ 1043_1044_ 1045_1046_ 1047_1048_ 1049_1050_ 1051_1052_ 1053_1054_ 1055_1056_ 1057_1058_ 1059_1060_ 1061_1062_ 1063_1064_ 1065_1066_ 1067_1068_ 1069_1070_ 1071_1072_ 1073_1074_ 1075_1076_ 1077_1078_ 1079_1080_ 1081_1082_ 1083_1084_ 1085_1086_ 1087_1088_ 1089_1090_ 1091_1092_ 1093_1094_ 1095_1096_ 1097_1098_ 1099_1100_ 1101_1102_ 1103_1104_ 1105_1106_ 1107_1108_ 1109_1110_ 1111_1112_ 1113_1114_ 1115_1116_ 1117_1118_ 1119_1120_ 1121_1122_ 1123_1124_ 1125_1126_ 1127_1128_ 1129_1130_ 1131_1132_ 1133_1134_ 1135_1136_ 1137_1138_ 1139_1140_ 1141_1142_ 1143_1144_ 1145_1146_ 1147_1148_ 1149_1150_ 1151_1152_ 1153_1154_ 1155_1156_ 1157_1158_ 1159_1160_ 1161_1162_ 1163_1164_ 1165_1166_ 1167_1168_ 1169_1170_ 1171_1172_ 1173_1174_ 1175_1176_ 1177_1178_ 1179_1180_ 1181_1182_ 1183_1184_ 1185_1186_ 1187_1188_ 1189_1190_ 1191_1192_ 1193_1194_ 1195_1196_ 1197_1198_ 1199_1200_ 1201_1202_ 1203_1204_ 1205_1206_ 1207_1208_ 1209_1210_ 1211_1212_ 1213_1214_ 1215_1216_ 1217_1218_ 1219_1220_ 1221_1222_ 1223_1224_ 1225_1226_ 1227_1228_ 1229_1230_ 1231_1232_ 1233_1234_ 1235_1236_ 1237_1238_ 1239_1240_ 1241_1242_ 1243_1244_ 1245_1246_ 1247_1248_ 1249_1250_ foo.txt
$ pgrep -af 'foo.txt'
1148 vi 1_2_3_4_