The speaker in the video has a good point. I have to agree with whoever said he was making it too complicated. And he was passing over some of the concept.
Accuracy is a standard applicable primarily to a specific problem, and secondarily to a weapon or shooter.
F'rinstance, the ability to defend against a human attacker requires a hit within about a six inch circle, generally centered high on the chest. At three feet, the problem is smaller in that a greater mis-alignment in aim is allowed than at twelve feet (or 300 yards). The requirement to score well is also defined by accuracy, be it precision rifle, pistol or shotgun. Also the exact shooting 'game' must be considered; International Rapid Fire has different requirements than Free Pistol.
It can be applied to a firearm. "This" pistol (this particular example, not the model) will not mechanically fire with sufficient precision to meet the requirements of [enter specific discipline here
]. An example of this is a 'as issued' Government pistol, either the old M1911A1 or the M9. Neither pistol were match grade Bullseye pistols as issued, but after 'accurizing', either will shoot amazingly small groups with a trained marksman. However, as issued, the accuracy is suitable for self-defense use.
As an advancing shooter - and all of us desire to 'advance', do we not? - one expects a certain level of competence in marksmanship after 'X' hours of instruction and practice, and a higher level after twice that long.
The video was demonstrating 'eight ring' accuracy (on the Prehl or B27 target) is sufficient for self-defense. The accuracy level is either there or not; but an X-ring hit is not 'greater' than an eight-ring hit.
I'll disagree with one of the posters on this thread. When shots are being fired at one, the standard of accuracy is not stricter; the same 'shot in the 8 ring' will suffice. However, it will be more difficult to keep a clear head and make the shot.