Earlier quoted context omitted.
Sys V init was not a standard. Is it in POSIX? I can't find it.
One of these init systems is run by a guy that is openly hostile to POSIX, the other can be found on several different operating systems and has been around forever. hmmm...
Only some Linux distros use SysV init and they're not any of the big players (Fedora/RH was the distro creating systemd), Ubuntu adopted systemd as the default 5 years ago, SUSE did the same 6 years ago, Debian 5 years ago. Almost everything else is a hobbyist OS (I've never seen Gentoo or Slackware in production anywhere else than at small companies where the server was on the critical path for maybe several tens of thousands of dollars, at best, which is peanuts on a global scale) or a niche OS (Alpine is used 95% as a container distro, and who freaking cares about the init system in a container? :-) ). Basically anyone who "puts there money where their mouth is" uses systemd.
SysV init was never adopted by BSD.
I think Solaris used to use it but it's been using Service Management Facility for the past 16 years.
HP/UX and AIX use SysV init, I think, but they're so vanishgly rare that 99% of developers and sysadmins out there could have the most successful careers in history and both HP/UX and AIX could be nuked from history for all they care.
And my point was that nobody even bothered to standardize SysV officially, though it was supposed to be a standard. That's how little everyone cared.
Poettering might be annoying, but he cares, he's opinionated and is actually knowledgeable. I've been using his software for a while and it's quite solid and his vision makes sense. POSIX isn't enough for a modern operating system.