I agree. It might be simple physics. As Frattin said on the radio, he just overpowered the guy. The photos show that at the point of the most violent part of the contact Frattin's feet are still on the ice. However, Wehrs goes down and that energy has to go somewhere, so likely up. One guy bounced one way, the other went the other way.
However, Wehrs's head probably hits on Frattin's shoulder and so that may still be cause for the contact to the head discipline.