Exactly... some people need to give Dave a break here! He never claimed this was a list of the hardest punchers... it's a list of who he has been hit hardest by, in his experience! These kind of lists are always lop-sided. He also mentioned that a few of them (i.e. AJ), didn't go that hard in sparring, whereas he's sure if he faced him in a real fight, he would hit a lot harder! He knows that Chisora doesn't hit harder than AJ in a real fight. When you take this into account, I'm not that surprised Chisora is number one... Chisora only knows how to fight one way, and I imagine he does exactly the same in sparring. It's just not in his instinct to "go easy".
That might actually make sense. I'm no scientist/neurologist, but pain comes from the brain right? And that's where you are getting hit. Therefore, the brain is obviously bound to be not working properly in those moments. Plus there's adrenaline involved. Allen might have been super high on adrenaline when facing certain fighters, and not so much when facing others. Humans are complex creatures. We're not punching machines that can actually calculate how much power was involved.