I think that is all very good information, and there are bits & pieces of it that are probably applicable to most everyone. But I'll tell you, that is way more in depth than I get with my hunting guns.
I have a very realistic expectation of how I shoot and what I expect of my hunting rifles vs my shooting ability. That is a 2" 3-shot group at 100 yards. If I can do better than that, I'm happy, if I'm in the 2" - 3" range, then I'll work on the gun with a different bullet and load until I get those 3 shots under 2".
If it's worse than 3", and I have only ever had one gun that shot that poorly, I'm probably not going to spend a whole lot of time on it.
Guns are inherently accurate enough for hunting purposes, or they wouldn't be on the market. MOST firearms companies are not going to let a gun out of the factory that doesn't shoot reasonable groups. If your gun is patterning like a shotgun, something is wrong with it, and in most cases I'm not going to spend my time on an inaccurate gun.
One thing I never see anyone mention is a bent or misaligned barrel. They happen, I've seen them. People do a lot of dumb things with guns, and can cause a gun to malfunction in a myriad of ways. Those are guns I'm not interested in.