Then there are cases where a service is intentionally shut down for a critical operation of some kind but a client connects to the socket, auto-starting the service in the middle of the critical operation.

Debian hit this some years ago in its conversion to systemd. It took the existing van Smoorenburg rc notion of temporarily stopping services during a package upgrade and translated that in the straightforward manner to systemd units. People started hitting services that got restarted in the middle of a package upgrade, causing various unwanted side-effects. So the Debian mechanism had to be changed to detect the existence of systemd and stop/start the socket units as well as, or sometimes instead of depending from the service, the service units.

Package upgrades are not the only places where one hits this. It is important that socket/path/automount/timer units be stopped as part of the shutdown process, not just service units, otherwise one can end up with shut down services being started back up by the sockets/paths/automounts/timers late in the shutdown process, potentially deadlocking it, and at least lengthening it by a significant amount.