IMHO supporting several init tools does more harm than good to any distribution. Its a lot of extra effort that few users will even notice.

Traditionally we used a script to boot. Those of course looked different in each distribution, but the "init tool" was the same. Then we switched over to sysv init (and man did people complain about this overcomplicated mess of symlinks!), yet pretty much all distributions switched to that. Of course they shipped widely different init scripts, but the tool was pretty much the same everywhere. The Linux Standard Base even prescribed the sysv init and any compliant distribution had to use that. We never had a time where distributions offered options wrt. init tooling.

I doubt the portability issue reporting from gentoo makes any difference whatsoever for the BSDs. They come up with all kinds of Linux compatibility stuff and that gets them the software they want.