If you already have it installed, it continues to work. If you create a new profile and try to install it, you'll find you can't.

I reported the man page problem and the GNU grep maintainer has installed a patch: https://debbugs.gnu.org/cgi/bu...

This is the POSIX synopsis for grep:

grep [-E|-F] [-c|-l|-q] [-insvx] -e pattern_list
              [-e pattern_list]... [-f pattern_file]... [file...]

grep [-E|-F] [-c|-l|-q] [-insvx] [-e pattern_list]...
              -f pattern_file [-f pattern_file]... [file...]

grep [-E|-F] [-c|-l|-q] [-insvx] pattern_list [file...]

It describes what all of that means in detail.

The GNU man page is incorrect when it says egrep and fgrep were not standardized by POSIX. They were included in POSIX.2-1992 but marked as obsolescent. When POSIX.2-1992 and POSIX.1-1996 were merged (along with the Single UNIX Specification) to form POSIX.1-2001 the obsolescent features from POSIX.2-1992 were removed.

Don't know where you got 2015 from. The Open Group first certified OS X (as it was called then) as UNIX in 2007.