The distfile for f2fs-tools at https://dev.gentoo.org/~zlogene/distfiles/sys-fs/f2fs-tools/ does not reflect the actual files at https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git/tree/ Specifically, at least f2fs_format_main.c in the distfiles lacks the "compression" attribute, meaning it is not possible to enable compression on this filesystem. The version info and date appears correct, but the files are not.
Oops, support was added after 1.13.0. My bad.