True, but the difference between the point of impact of the second shot with iron sights and with scope sights should be minimized. Also, in many instances vertical dispersion is less of a problem than horizontal. For instance, if one misses a heart shot taken broadside vertically, it will still catch the lungs or break a leg. The same shot, deviating horizontally, will result in a gut shot or a clean miss.

Of course, with shots taken at close range, in rapid sequence, the point of impact deviation in either case would hardly be noticeable. I certainly never noticed it shooting elephant and buffalo with my scope sighted over and under .458 WM.