The thing about Sanji v King is that Sanji never proved to possess the AP to consistently harm King. He didn't manage to destroy Page 1 or X Drake in a short amount of time, so you know what that does precisely equate to when he tries to take on much more durable folks.
And since Killer managed to injure Kaido, he is 100% demolishing the suit and following a logical process any YC1 is meant to be capable of the same feat. Would be ridiculous if Killer's AP was a lot above YC1, no matter who the YC1 is.