Shin didn't THROW anyone, he sidestepped him. There was no "super dodge" Shin moved his body out of the way of Metz' body, arms move freely to the body and an extended arm with a knife does not mean that the rest of your body is immediately behind it. So unless your hands are directly connected to your shoulders and you stab someone in the shoulder, them moving the rest of their body out of the way is entirely feasible. 

That's why the knife would have either slipped out of his hand or came wrenching out, because the rest of his body moves freely from his hands.

Edit: Also, how would he be dragged towards Metz? He let go of the chain.