Aside from the gunners, the punt return players cannot head down field until the ball leaves the kickers foot or you get an illegal man downfield penalty.
Should be 2-3 seconds until the ball leaves the kickers foot so in that time our 200-230 lb players would have 260 lb+ guys firing off the ball at them. They have to at least try and block or the opponents will just block the kick. So yeah, a 200lb db standing still while someone running at them and outweighing them by 50+ lbs would get flattened.
I played up back on punt returns a bit in HS. It's ugly if one of those big guys goes unblocked, you just try and slow them down and redirect them but you're going to get hit.