Totally agree.

I assigned the App Groups ID to the bundle on developer account and even though it didn't worked. I'm still getting the warning [User Defaults] Couldn't read values in CFPrefsPlistSource<0x281cb9e80> (Domain: group.com.example.app, User: kCFPreferencesAnyUser, ByHost: Yes, Container: (null), Contents Need Refresh: Yes): Using kCFPreferencesAnyUser with a container is only allowed for System Containers, detaching from cfprefsd for using the same group id as UserDefaults suitName. Is it safe to just ignore this?

This is such a significant paradigm shift. I wish Apple had addressed this more thoroughly at WWDC23, rather than giving us those 'rest of the freaking owl' kind of examples.