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.
Unless I missed some other details (this thread has gone on for a long time) he wrote he used a "Leupold 5HD" and a "Conquest" scope. He does not specify the magnification or objective lens size of either, so there could be far more parallax than you're assuming, especially assuming a scope parallax-free at 150 yards.
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.
