mandoc.db keeps changing in 11.0-RELEASE?

[Doug McIntyre]

I've seen this happen on several FreeBSD 11.0-RELEASE systems I run.

I have 'freebsd-update cron' running each night.

And from time to time, I'll get a whole slew of notices about mandoc.db
changing. Ie. this system is already at 11.0-RELEASE-p5..
$ freebsd-version
11.0-RELEASE-p5

And for a notice I get via email..

Looking up update.FreeBSD.org mirrors... none found.
Fetching metadata signature for 11.0-RELEASE from update.FreeBSD.org... done.
Fetching metadata index... done.
Inspecting system... done.
Preparing to download files... done.

The following files will be updated as part of updating to 11.0-RELEASE-p5:
/usr/share/man/mandoc.db
/usr/share/openssl/man/mandoc.db

And of course, I could ignore it, and each night it'll bug me, or I can
update it with 'freebsd-update install', and the notice goes away.

So, what's up with the 11.0 build process that mandoc.db keeps getting
touched or whatever it is?

This happens on most of my 11.0-RELEASE machines from time to time.