Created attachment 422268 [details] groff-1.22.2-r1.ebuild: >=sys-apps/texinfo-4.7-r1 dependency removed groff-1.22.2.tar.bz2:/groff-1.22.2/doc/Makefile.in states that "info files are distributed with the groff package, so makeinfo is usually not needed". makeinfo tool is included in texinfo, which is therefore not a dependency.
looks like an old bug fix that got out of hand http://gitweb.gentoo.org/repo/gentoo.git/commit/?id=03c319c399279ce9446557fad62a359592d6a1f0