Yeah that sounds about right to me. It's like wondering how a boxer can take a punch to the gut and not get winded. They are trained for it, and know how to absorb the contact. The RB's are the same way.
And the more I think about it, unless the rules change there is no downside to running this offense. You can barely touch the QB as it is or, it's a 15 yard penalty. You can't just teach your D to go in the backfield and hit everybody, because you would be walking a fine line for getting a roughing penalty if you don't time it perfectly.