> This is obviously not about systemd, so what's up?

It absolutely is about systemd. It's a project that's famous for having almost no limits to its scope, and is highly willing to break existing conventions in order to achieve a more sensible overall system architecture. Having a specialized (and relatively undiscoverable) procedure for safely editing config files is the kind of ugly hack I'd expect systemd to be strongly against. As far as I can tell, the hack in systemd's case seems to be motivated entirely by wanting to avoid problems caused by poorly-behaved package managers. It would be entirely in-character for systemd devs to just tell people to fix their package managers, and that would be the better outcome in the long run. So I'm puzzled why any systemd proponent wouldn't regard this status quo as a wart that needs to be on their roadmap to fix properly.