This isn’t magic, we can feel what each other are feeling even at some distance. The only reason it feels at all mystifying is because our dogmas about the nature of thought separate feelings into a separate category of triviality, rather than taking them seriously as phenomena produced by our body and environment in concert.

"They will pull their shirt down to cover rear end but it’s completely impossible they could have seen the observer, they can sense it."

Women usually have better peripheral vision than men. Also we hear and smell many more things, than we consciously notice.

Males of course can't notice if women adjust clothing when they aren't looking, if they adjust clothing sufficiently often then it's as if they adjust clothing whenever you're looking

That plus subconscious monitoring of nearby males and how they move, if you're a woman roughly speaking if one is in your blind spot it's sufficiently probable he would be using that chance to look at you (or parts of you).