What App Permission would allow an app to display over Lock Screen?

I've been play this game TopHeroes and I noticed that when I press the side button to lock my phone and then go to unlock it again, it displays itself over the lock screen (similar to Google Maps). I contacted their support and got told it was an Andriod update that caused this. However, doing some googling, it seems this issue is more than a year old (as seen on their discord help and reddit). Some reseach would suggest android.permission.WAKE_LOCK might cause this behavior. But if ya'll have a better idea of what "andriod update" or "andriod setting" I need to adjust, that would be helpful.