"One shot stop" is totally irrelevant.

No one with any training or a lick of common sense is going to shoot an assailant once, and then stop and wait to assess the results.

Instead, anyone with any training or common sense is going to keep shooting until the assailant goes down, or until the slide locks back, which ever comes first.

It might make a bit more sense to discuss bullet performance in terms of a failure to stop drill. Are you gonna shoot him twice center of mass and then transition to a head shot? Or are you going you shoot him a couple more times center mass before considering a head shot if he won't go down?

Either way you're not going to stop with just one or two shots, unless he's obviously going down.