Dan,
Yep, exactly--but there are many assumptions in parallax calculations, especially that the shooter can recognize it. Many don't. Country boy only states that he adjusted the rear focus on the scopes, which may indicate he doesn't know how to check for parallax. I asked him specifically about that at one point, but he never really responded.
I was answering Youper's question, not country boy's, in that post.
FWIW though I raised the question with country boy earlier about adjusting the eyepiece focus rather than parallax, and he confirmed that he was both aware of the difference between eyepiece focus and parallax adjustment, and that he had adjusted for parallax.
Add a little wind-drift to more parallax than the possibility you used as an example, and there could easily be 2+ inches of error at 200 yards.
I made the point earlier that I didn't think that parallax was the sole problem, if it was the problem at all. There are a range of other possibilities, including wind, and including the possibility that a number of issues, perhaps including parallax, are combining to produce the observed result.
