Again I get the claim that he had his hands down and everything but when he actually got beat in the 3rd it was a time when he was evading and trying to defend and the initial punch that rocked overeem was one where his hands were not down. So I don't think him having his hands down was the actual precursor to him getting KO'd.
Oh and btw... I really hope JDS or someone else knocks bigfoot out cold. I just don't like him.