Isn't it clear that when the force of the punch moves you and breaks your resistance that's a knockdown? It doesnt have to stun you, if it's the glovr or the body, when it's the force that beat you. Shavers-Holmes 2nd knockdown Zab-Floyd Hammer-Ortiz Those are some examples
If I remember rightly in the 9th round Holmes went down from a sloppy right hand from an exhausted Shavers. It looked more a slip to me but it could've been ruled a 2nd knockdown, I'd have to see it again it's right near the end of the round I believe for reference.
