Most of these discussions, hinge on single bullets, striking this, or that.
Firing one, or two rounds, then evaluate? If it ever was, to my mind, a factor, is nonsensical.
SHOOT HIM A LOT! Comes to mind. So other factors come in to play, amount of rounds carried in a given pistol, is significant. As is the recoil of a given bullet, moving the muzzle off target, so many imponderables!
After action reports, as to time of day, clothing worn, mind set, you could go on and on.
Only things you, the pistol carrier, can control count. Calibre, bullet type and weight, amount in a given pistol, even sights, and trigger release weight, all need to be taken into consideration. Even such factors as keeping away from certain areas of a City, how you carry your self defense pistol (re rapid deployment) holsters, mode of dress.
Lady Luck is in there somewhere also! Managers, and various, and sundry supervisors like to say things like "The big picture" And it is, a big picture.