like, are all guys really this sensitive to breasts being pressed against them or what?
The proof of concept is on you.
If you put forward a theory its your responsibility to prove it
You saying you've really never seen guys freak out in anime when girls press their chest to the guys arm, back, or chest?
It's happened to me once or twice before back in high school, but I never freaked out. I obviously enjoyed it, though I hid it pretty well to avoid looking like a letch.
Not like anime at all, but it is a nice feeling and different from most of the other contacts you get.