How the hell would you have the same AP when your body isn't physically in peak condition because it was injured? Again this was already stated in the arlong arc. Zoros attacks were weaker because he was previously damaged by mihawk hence arlong wanting to kill Zoro right then in their because he realized that if Zoro wasn't weakened he would be finished lol
Many finishers from the heroes happen when someone is on deaths door and put all they have into it.
Hajrudin failed a strength clash, broke his arm in several places, then muscled through that same strength clash, so he went from having less AP at full health to more AP when his arm was destroyed. Many such cases throughout the series.