This all makes sense except that part about an off the shelf rifle being as accurate as the hunter. Those two things are not related. Accuracy errors are cumulative, so to say that the rifles is more accurate than the shooter does not make sense. If the rifle is a 2MOA weapon and the shooter is a 3MOA shooter, that's 5MOA. You say as much later in your post, but people need to stop thinking that an inaccurate shooter makes an inaccurate rifle moot. The exact opposite is true. A poor shot needs all the help they can get. The opposite is also true. The less accurate the rifle, the more skilled the shooter needs to be, but no matter how good the shooter is they can't make a rifle more accurate than it is. All they can do is reduce the accumulation of accuracy flaws.
I don't have any scientific evidence to back it up, but I disagree with the statements in bold. If accuracy errors are simply cumulative in that way, how would one explain the vast number of 1-2MOA claims? Are the rifles actually .5 MOA with a bunch of closet benchrest shooters pulling the triggers? The chance of a rifle throwing a shot in the exact same direction as the shooter errors in aim/trigger pull/follow through would be extremely unlikely to occur once. For it to happen enough to effect an entire sampling of data or "groups" would be impossible.