Forgotten MFC (was: make delete-old does not delete old devd(8) config)

> I guess the following commit is missing in stable/14:
> <https://cgit.freebsd.org/src/commit/?id=272b4b764bdfb563f655da37ef9ec8c01c77f386>

I've been thinking about it and got curious: how did this kind of happened?  As
far as I know (and read in the Commiter's Guide), MFC'ing is done by manually
picking some commits and cherry-picking them to another branch (in this case, to
-STABLE).  Also, a special field in commit message can be set: "MFC after:" to
get an email which will remind about MFC'ing this commit.  So as I can see, this
commit didn't have such a field and it simply was missed and forgotten?  It's
been a while (more than a year, and the longest delay before MFC I personally
saw is about 1 month) and I wonder would that commit never been MFC'ed into
14-STABLE branch if nobody reports about it?  I guess it _would_ be included in
the upcoming release (branched from -CURRENT), but really curious how would
that be with -STABLE.  And if it really would be lost, how do developers usually
deal with that?  Apart from cases when the problems are reported, do they
manually walk through the commits to pick up some forgotten ones?

And also I'm interested: what software does the parsing of a commit message for
"MFC after:" field and schedules the email reminder?  Tried to do some search
in /usr/src, but didn't find much.

Thank you,
Artem