I would argue that if a gun has real imperfections it would show up in the first 3-5 shots. Besides I usually shoot 4 shots into one hole and get one flier at 50 y. Does this prove that the gun is faulty? No, it was either me, a bad pellet or some random variable like a gust of wind.
I don’t need to shoot 10 shots to determine my gun’s accuracy. All 10 shots does is makes a slightly bigger hole. Three to five shots tells me more of the story.
And I agree that when shooting slugs, if you have a 100 yard, 3 shot group at 0.16” why waste seven more shots? Those things are ’spensive!