zesty partner-images/Docker rootfs tarballs much larger than expected

The "zesty" rootfs tarballs under https://partner-images.canonical.com/core/ appear to be much larger than they likely ought to be.

Simple comparison, to illustrate: (https://partner-images.canonical.com/core/zesty/20161128/ vs https://partner-images.canonical.com/core/yakkety/20161121/)

  ubuntu-yakkety-core-cloudimg-amd64-root.tar.gz 21-Nov-2016 20:37 39M

  ubuntu-zesty-core-cloudimg-amd64-root.tar.gz 28-Nov-2016 09:02 138M

As shown above, the zesty tarballs are ~100M larger than the yakkety tarballs (and that's the gz-compressed sizes, too)!

Comparing just the package lists (ignoring version numbers for a simpler diff):

  $ diff -u <(curl -fsSL 'https://partner-images.canonical.com/core/yakkety/20161121/ubuntu-yakkety-core-cloudimg-amd64.manifest' | cut -d$'\t' -f1) <(curl -fsSL 'https://partner-images.canonical.com/core/zesty/20161128/ubuntu-zesty-core-cloudimg-amd64.manifest' | cut -d$'\t' -f1)
  --- /dev/fd/63 2016-11-28 12:22:08.293033600 -0800
  +++ /dev/fd/62 2016-11-28 12:22:08.294033574 -0800
  @@ -1,89 +1,265 @@
   adduser
  +apparmor
   apt
   base-files
   base-passwd
   bash
  +bridge-utils
   bsdutils
  +busybox-initramfs
  +bzip2
  +ca-certificates
  +cloud-guest-utils
  +cloud-init
   coreutils
  +cpio
  +cron
   dash
  +dbus
   debconf
   debianutils
  +dh-python
   diffutils
  +distro-info-data
  +dnsmasq-base
  +dosfstools
   dpkg
   e2fslibs:amd64
   e2fsprogs
  +efibootmgr
   findutils
  +fwupdate
  +fwupdate-signed
   gcc-6-base:amd64
  +gdbserver
  +gdisk
  +gettext-base
   gnupg
   gnupg-agent
   gpgv
   grep
  +grub-common
  +grub-efi-amd64
  +grub-efi-amd64-bin
  +grub-efi-amd64-signed
  +grub-pc-bin
  +grub-xen-bin
  +grub2-common
   gzip
   hostname
  +ifupdown
  +init
   init-system-helpers
  +initramfs-tools
  +initramfs-tools-bin
  +initramfs-tools-core
  +initramfs-tools-ubuntu-core
  +iproute2
  +iptables
  +iputils-ping
  +isc-dhcp-client
  +klibc-utils
  +kmod
  +less
   libacl1:amd64
  +libapparmor-perl
  +libapparmor1:amd64
  +libapt-inst2.0:amd64
   libapt-pkg5.0:amd64
   libassuan0:amd64
   libattr1:amd64
   libaudit-common
   libaudit1:amd64
   libblkid1:amd64
  +libbsd0:amd64
   libbz2-1.0:amd64
   libc-bin
   libc6:amd64
   libcap-ng0:amd64
  +libcap2:amd64
  +libcgmanager0:amd64
   libcomerr2:amd64
  +libcryptsetup4:amd64
   libdb5.3:amd64
  +libdbus-1-3:amd64
   libdebconfclient0:amd64
  +libdevmapper1.02.1:amd64
  +libdns-export162
  +libedit2:amd64
  +libefivar0:amd64
  +libestr0
  +libexpat1:amd64
   libfdisk1:amd64
  +libffi6:amd64
  +libfreetype6:amd64
  +libfuse2:amd64
  +libfwup0:amd64
   libgcc1:amd64
   libgcrypt20:amd64
  +libgdbm3:amd64
  +libglib2.0-0:amd64
  +libgmp10:amd64
  +libgnutls30:amd64
   libgpg-error0:amd64
  +libgssapi-krb5-2:amd64
  +libhogweed4:amd64
  +libidn11:amd64
  +libip4tc0:amd64
  +libip6tc0:amd64
  +libiptc0:amd64
  +libisc-export160
  +libjson-c3:amd64
  +libk5crypto3:amd64
  +libkeyutils1:amd64
  +libklibc
  +libkmod2:amd64
  +libkrb5-3:amd64
  +libkrb5support0:amd64
   libksba8:amd64
  +liblockfile-bin
  +liblockfile1:amd64
   liblz4-1:amd64
   liblzma5:amd64
  +liblzo2-2:amd64
  +libmnl0:amd64
   libmount1:amd64
  +libmpdec2:amd64
   libncurses5:amd64
   libncursesw5:amd64
  +libnetfilter-conntrack3:amd64
  +libnettle6:amd64
  +libnewt0.52:amd64
  +libnfnetlink0:amd64
  +libnih-dbus1:amd64
  +libnih1:amd64
  +libnl-3-200:amd64
  +libnl-genl-3-200:amd64
   libnpth0:amd64
  +libnss-extrausers
  +libnss-myhostname:amd64
  +libp11-kit0:amd64
   libpam-modules:amd64
   libpam-modules-bin
   libpam-runtime
  +libpam-systemd:amd64
   libpam0g:amd64
  +libparted2:amd64
  +libpcap0.8:amd64
   libpcre3:amd64
  +libpcsclite1:amd64
  +libpng16-16:amd64
  +libpopt0:amd64
   libprocps6:amd64
  +libpython3-stdlib:amd64
  +libpython3.5-minimal:amd64
  +libpython3.5-stdlib:amd64
   libreadline7:amd64
  +libseccomp2:amd64
   libselinux1:amd64
   libsemanage-common
   libsemanage1:amd64
   libsepol1:amd64
  +libslang2:amd64
   libsmartcols1:amd64
   libsqlite3-0:amd64
   libss2:amd64
  +libssl1.0.0:amd64
   libstdc++6:amd64
   libsystemd0:amd64
  +libtasn1-6:amd64
   libtinfo5:amd64
   libudev1:amd64
   libustr-1.0-1:amd64
   libuuid1:amd64
  +libwrap0:amd64
  +libxtables11:amd64
  +libyaml-0-2:amd64
  +linux-base
   locales
  +lockfile-progs
   login
  +logrotate
   lsb-base
  +lsb-release
   mawk
  +mime-support
  +mokutil
   mount
   multiarch-support
   ncurses-base
   ncurses-bin
  +net-tools
  +netbase
  +netcat-openbsd
  +nplan
  +openssh-client
  +openssh-server
  +openssh-sftp-server
  +openssl
  +parted
   passwd
   perl-base
   pinentry-curses
  +ppp
   procps
  +python3
  +python3-blinker
  +python3-cffi-backend
  +python3-chardet
  +python3-configobj
  +python3-cryptography
  +python3-idna
  +python3-jinja2
  +python3-json-pointer
  +python3-jsonpatch
  +python3-jwt
  +python3-libapparmor
  +python3-markupsafe
  +python3-minimal
  +python3-oauthlib
  +python3-pkg-resources
  +python3-prettytable
  +python3-pyasn1
  +python3-requests
  +python3-serial
  +python3-setuptools
  +python3-six
  +python3-urllib3
  +python3-yaml
  +python3.5
  +python3.5-minimal
   readline-common
  +realpath
  +resolvconf
  +rsyslog
  +seccomp
   sed
   sensible-utils
  +shim
  +shim-signed
  +snap-confine
  +snapd
  +squashfs-tools
  +sudo
  +systemd
  +systemd-sysv
   sysvinit-utils
   tar
   tzdata
  +u-boot-tools
  +ubuntu-core-config
  +ubuntu-core-launcher
  +ubuntu-core-libs
  +ubuntu-core-snapd-units
  +ubuntu-fan
   ubuntu-keyring
  +ucf
  +udev
   util-linux
  +vim-common
  +vim-tiny
  +watchdog
  +whiptail
  +wpasupplicant
  +xz-utils
   zlib1g:amd64