

That would be a pretty big security hole in iOS if that was allowed, but it isn’t. Notification and other UI elements are rendered on top of the underlying app, which does not have access to or cannot see the full screen’s canvas. We can see practical implementations of this “snapshot” test feature in code:
I was asleep in bed one night many years ago and heard a loud bang, startling me awake. I thought for sure somebody was trying to break in a window or something. Went out, checked the house, nothing amiss. Went outside, checked around for any signs of something being off, not a thing. I then sat in my living room for 30 minutes trying to decide if it was a dream or if it would happen again. Still, nothing. I went back to sleep.
The next morning I made coffee and sat down at my MacBook Pro. It was an older model but I immediately noticed something was wrong. The entire laptop was elevated off the table slightly. The battery had apparently expanded in the middle of the night and with enough force ripped the bottom aluminum cover through three of the screw holes. Found the source of the noise, and immediately took it for disposal.
I was very lucky it didn’t catch fire, although it would have quickly solved my midnight mystery.