The theory looks flawed to me as the true finishing blow to Kaido will presumably be inflicted by Zoro. Sure, that does not necessarily implicate that Luffy cannot deal the one that defeats him and he is still alive until Zoro kicks in, but the theory looks flawed in the premises hence less likely even if Big Mom also won't be defeated with Kidd's blow hence it would simply constitute a combo lacking that level of emphasis, therefore less intense to portray.