It is often too general and can produce bad results with make makeplist. For example, in mail/aerc it produces bogus entries like
man/man5/%%GO_PKGNAME%%-sendmail.5.gz
since GO_PKGNAME=aerc there. AFAICT this was only ever really useful for Go libraries, so I think we should drop it now.
Only 2 ports appear to use it currently which are easily fixed.