First, I read that case (the crap ton more ammo guy). He hit the assailant a bunch of times. Many were non-survivable wounds, but the guy didn't go down till hit in the head. He was using excellent marksmanship, and a .45. The perp was a Swiss cheese by the time the fight was done - a human bag that would not hold blood. But he did not bleed out fast enough to end the fight.
Second, that is only one of the cases I am aware of wherein ammunition capacity, a backup gun, and/or reloads mattered.