I get it now: gnome-netstatus takes the largest available icon and scales it vertically, without keeping the aspect ratio. See src/netstatus-icon.c, the code of netstatus_icon_scale_icons (passes retain_aspect=FALSE to scale_pixbuf when scaling signal icons) and netstatus_icon_lookup_icon_theme (passes 1000 as the desired size to gtk_icon_theme_lookup_icon to get the biggest one).
I get it now: gnome-netstatus takes the largest available icon and scales it vertically, without keeping the aspect ratio. See src/netstatus- icon.c, the code of netstatus_ icon_scale_ icons (passes retain_aspect=FALSE to scale_pixbuf when scaling signal icons) and netstatus_ icon_lookup_ icon_theme (passes 1000 as the desired size to gtk_icon_ theme_lookup_ icon to get the biggest one).