I'm pretty average, probably below average, and I can do a lot better than that. Like 2 to 3 MOA at 100 meters with American Eagle 55gr out of my 6920.
I look at accuracy as a series of Venn diagram type overlapping circles. The rifle and ammunition capability is one circle with an which may not be centered on the target due to poor zero or incorrect elevation correction. From there the shooter's fundamentals are another circle,
and their wind calling ability a wide and slightly diagonal oval due to cross wind jump.
So say the rifle is zeroed 2 MOA left, the ammo can do 4 MOA and a shot ends up being on the very left of that, then the shooter's ability is 4 MOA and a shot ends up on the left edge of that, and the wind pushes the round 2 MOA left the round could impact 8 MOA left. Then, with the exception of the zero being left, all those factors could shift to the extreme in another direction leading to shitty groups.
That's my take on it. 12 MOA shooters probably don't put as much thought into it. Or maybe I'm overthinking it.