> they cannot have “automatically join” disabled
They can on my AT&T iOS 16.4 device. I was able to disable auto-join on the two AT&T ones. I didn't need to delete a network to enable the "done" button from the edit screen - the state I toggled for auto-joining the managed networks persisted even if I hit cancel on the edit screen.
I don't like that they're there and auto-join is on by default, but it does appear that can be turned off.