It's totally buggy unfortunately, and has been for years. Also, all time limit features are circumventable by switching time zones for example.
Sometimes apps will randomly appear to have time limits which the parent has never set also.
It's really a bugfest through and through.
This is crazy, friends told me apple was good on this, before we had to get a phone for our self, I now think they simply don't understand whats happening. It looks fine to non-tech parents i guess.
The question is, what can be used as an alternative?
I had first tried an old Android phone, but theres no way to disable app store, so kid figured out he can watch app store videos with no limit...
Android's not better, unfortunately. We also tried them for the kids, and most protection software back then simply could be killed by rebooting the phone and overloading the phone a bit immediately after reboot.