What if the belt can't be removed? I've seen pants that have a "belt", but, though it has loops on most of the pants, it's secured to the pants on the back. Or what if it would be the case that removal of the belt would cause the pants to fall?

The last few times I went through an ATR-AIT, I had a lot of time on my hand and put my shoes on slowly and watched the screen and these pat-downs. It sounded like you were seeing anomalies about 10-15% of the time. When I was watching (admittedly a much smaller sample), it looked closer to 40-50%. But what I found interesting is that I'd say in about half of those cases, the passenger wasn't touched at all. In most of those, the reason was clear: the anomaly was in an area of bare skin or head. But in some it was quite mystifying to me how the area could be cleared without any contact (no, it wasn't a situation of "skin tight" clothing). Can you explain this?

And I do agree that there's no way that you could have known if the machine were storing images since SSD storage is tiny and could have been anywhere: just open an access door, remove a 500GB SSD device, and you have the images. Or some wireless mechanism (less likely). That being said, I can't see a reason to store the images without recording, for each that had an anomaly, what that anomaly turned out to be. And it's clear no such record is being made.