The files I have installed are: /usr/share/man /usr/share/man/man5 /usr/share/man/man5/depmod.d.5.bz2 /usr/share/man/man5/modprobe.d.5.bz2 /usr/share/man/man5/modules.dep.5.bz2 /usr/share/man/man5/modules.dep.bin.5 /usr/share/man/man8 /usr/share/man/man8/depmod.8.bz2 /usr/share/man/man8/insmod.8.bz2 /usr/share/man/man8/kmod.8.bz2 /usr/share/man/man8/lsmod.8.bz2 /usr/share/man/man8/modinfo.8.bz2 /usr/share/man/man8/modprobe.8.bz2 /usr/share/man/man8/rmmod.8.bz2 As you can see "modules.dep.bin.5" did not get compressed.
Generally, ebuilds are not responsible for compressing man pages. Portage takes care of that. I believe portage has some logic that intentionally does not compress files under a certain size.
See line 5 of prepman. https://gitweb.gentoo.org/proj/portage.git/tree/bin/ebuild-helpers/prepman
generally speaking, ebuilds are not responsible for compressing their docs. in this case, certainly kmod is not. that said, this is WAI and is entirely a feature. portage stopped auto-compressing small files a while ago because: (1) the size often goes *up* (2) it increases runtime overhead to save literally a few bytes to this specific file: $ cd /usr/share/man/man5 -rw-r--r-- 1 root root 18 Mar 7 14:36 modules.dep.bin.5 $ bzip2 < modules.dep.bin.5 | wc -c 58 so had portage compressed it, you'd be using 40 extra bytes, and it'd be slower
