The thing is, in a lot of these case it's easy to sit on the safe side of the ropes trying to imagine whether or not a fighter could have got up, whether or not he tried to get up, how hurt he really was, etc. etc. In a lot of cases the reality is probably not the same as it looks to us, and I give most of them a big benefit of the doubt when I know they got hit with a punch that probably would kill or maim the average man anyway.
People get thrown flying from cars 50 feet and do the same thing before walking away unharmed. So what? Their minds and in this case the fighters are obviously in another place irregardless of their momentary peek of the world before "giving in". They're for all intents and purposes out, just not stone cold out.
A lesson that I learn in endurance sports, is that everybody has quit in them somewhere, including the bravest people. Everybody takes their personal dive at some point, even if it is by a fairly circuitous route.
Brian London against Ali. Fair enough he was hit by a 14 or 15 punch lightning fast combination, but I think realising he was badly outclassed he just decided he'd be better off staying down. London has virtually admitted as much since.