Re: Groff
You're quite right, once all man pages were compatible with mandoc, then groff was removed from base in 2017: https://github.com/freebsd/freebsd-src/commit/738919c0391b99947b758d85f6a8636be1886fbb
But the first release this took effect was indeed 12.0R in December 2018. Among other switchers to mandoc, macOS removed groff in 2022 with Ventura, and OpenBSD (where mandoc originated) all the way back in 2011: https://undeadly.org/cgi?action=article&sid=20110314142734
It helps that mandoc is ISC-licensed so more BSD-friendly, and simpler since it only needs to understand man pages rather than trying to do general typesetting.
I can see the reason for the confusion is that Liam's quoting a comment - about an advantage of pkgbase being that you could drop something like groff - which was made in November 2018 just before 12.0-RELEASE came out. Unfortunately reusing this example suggests groff is still in base, so the error is in the article itself. (Deleted my own comment because I can't edit it and don't want it appearing in search snippets or AI regurgitation and misleading people! Funnily enough I was using groff a few weeks ago in an almost fresh VM image and forgot this was one of the few packages I'd actually had to install.)