The INSOPTIONS variable should not be mentioned; install options should be set with the insopts function, but never by directly assigning INSOPTIONS. Also the -r option could be documented. Patch will follow.
Created attachment 417374 [details, diff] ebuild-writing/eapi: Update documentation of doheader in EAPI 5. Seems trivial enough, so I'll push this in a few days from now unless there are objections.
https://gitweb.gentoo.org/proj/devmanual.git/commit/?id=b7aff930e229a8dd82229f4495a8caa57625ce51