Honestly I’d prefer Touch ID on the power button rather than under screen. It’s good to have that dedicated tactile place, not on the screen, to put your finger for Touch ID. It’s easier/nicer having that place that you can easily and knowingly touch even without looking. And more importantly, it may even prevent you from getting duped into paying for something.
One example, I play a game that when the round ends and you’re trying to quickly restart a new round, the game will randomly deviously switch out the regular “restart round” screen with an in-app purchase screen at the EXACT moment that it knows people usually press the “restart round” button, with the “buy” button in the exact same spot as where the “restart round” button was, basically blatantly trying to trick them into purchasing something. Of course, the purchase has to then be authenticated by Touch ID before it can go through, and thankfully I have yet to be so spaced out that I put my thumb on the Touch ID button to authenticate it. But I have come close in my late night zombie stupors. And if they are still doing this, then I have to believe they are successfully tricking a good amount of people. But if the Touch ID digital button/area were on the screen, where one’s thumb is already, then there’s a much higher chance that more people will inadvertently authenticate, probably me included. So I think because it would be too easy to authenticate, Touch ID should stay off screen. Just my opinion.
edit- now I wonder if the people that the game I play is successfully tricking are mostly Face ID users since I believe Face ID only requires an on screen button tap to authenticate. 🤔