I'm saying that it did work perfectly fine and reliably for the common case of types oneshot and simple services. To expect it to work for type Forking services would be absurd since no mechanism would exist to even try to keep track of them. It's just a point to illustrate that systemd is not as intimately and irretrievably integrated with Linux features as some imagine.

Freezers were never used by systemd as part of its process tracking mechanism. And cgroup emptiness notification was unreliable under cgroups v1. So that's not wrong. It used some horrible mechanism where a binary is launched (!) when the cgroup becomes empty. And that can fail to happen under situations of low memory availability.

Related read is Jonathan de Boyne Pollard on cgroups:https://jdebp.uk/FGA/linux-control-groups-are-not-jobs.html