Reddit user informed regarding an unusual iOS 16 bug.
With it, he was able to activate the Always-On-Display feature in the iPhone 12 Pro. This was also confirmed by some other users. They note that they got a similar result as a result of the bug.
Formerly 9to5Mac showedHere is what the Always-On-Display toggle animation looks like in iOS 16, and it looked the same.
It is possible that this is a simple bug caused, for example, by a strong dimming of the wallpaper in dark mode.