Xorg was in the dep file as there was no Xlibs_support at the time of it's creation.
Documenting deps was standard in the beginning, before we had the dep tab in the appbrowser. And I am sure there are a lot of extensions created almost year ago that have old information in the info files. Even the "current" extension guidelines post gets out of date pretty quickly.
The major things I needed to do during this transition to one extension type are pretty much out of the way - repacking extensions for deprecated user.tar.gz, tce.installed perms, squashfs, etc. I will push revisiting old docs and info files of mine more to the front burner now that things have settled a little on my end.