It's headcanon though. You're making up any random excuse for Kizaru instead of just taking what happened on page at face value. What happened on page is that Kizaru got blasted by the punch and couldn't move, but you think "actually he wasnt really hurt at all and he just wanted to lie down on the floor because reasons xd"
It's not on me or anyone else to prove that Kizaru was fine, it's on you and his fans because the manga literally said he wasn't. So unless it's revealed to be a misdirect later on, i'm right just by taking it at face value.