Usually if the siege got to the point where attackers were IN YOUR TOWERs, then the next logical step would have been to either surrender or collapse the tower

Usually if the siege got to the point where attackers were IN YOUR TOWERs, then the next logical step would have been to either surrender or collapse the tower on the attackers to win a tactical victory. I am willing to bet $10000, that the number of sieges won or lost due to a staircase fight between knights is 0. Also I wonder what led to this hypothesis being created in the first place? That's a much more interesting question to me. Was it some eccentric historian just inventing it?