The phone can detect when it's in a dark place (i.e in a pocket). I think an option to turn off AOD while it's in your pocket is a good idea, because why have the screen on when it can't be looked at?
Since the S7 edge I use AOD and I always have it activated. And I have noticed that when the phone has been in my pocket for some time, it turns itself off. I can tell because when I take it out of my pocket I can see how it turns on again. And this has been like this for a long time as I have experienced.
I've tested this, and it doesn't on mine. I've found other things online about it not working as well, so I at least know I'm not alone. Mine will stay on 24/7 and doesn't turn off
After S10 this option is not available anymore. AOD is always active, for period, on tap to show but WILL NOT turn off ONLY when is in your pocket for example.
