tetex and the current texlive ebuilds use texlinks for creating symlinks from formats to engines, like latex -> pdftex in /usr/bin for texlive. The problem of handling files via texlinks is that those files are not under the control of portage, thus unmerging tetex or texlive leaves the symlinks around, pointing to nothing. I'm almost finished writing/importing the functions of texlinks in the eclass and creating the symlinks there, so that they will be in CONTENTS. The drawback of doing this is that if somebody had a previously installed version, that will cause collisions with those files that are on the system and don't belong to any package. As migrating to texlive will be a big step, I think it's the right time to fix that.
this is now fixed by using etexlinks from texlive-common.eclass
