A distinction has to be drawn between your ability to hold a sight picture (what I believe Bart is referring to) and your ability to get the shots to place that tightly on an actual target, especially at long range where wind, gun and ammunition limitations, bullet drop and even bullet-to-bullet variation all have effects you are challenged to resolve at 100 yards. You can prove your hold by shooting at 100 yards with a load suited to that range to eliminate those variables. When things are going well, shooting knots or sometimes bugholes at that shorter range isn't wildly uncommon, and I think we've all experienced that when our gun and loads were working well together.
This article describes a fellow who apparently can do it consistently. Most benchrest competitors hold sight pictures at that level of precision regularly. I don't know how close to that F-class shooters, specifically, do on hold, but don't see why they should be too much worse and Froggy shows they don't have to be worse.
I recall in Mid Tompkins's Long Range Firing School he told us 1000 yard wind changes faster than you can dial in adjustments finer than about half-moa, so he felt having sights with adjustments finer than that was pointless. If he picked up on a quarter moa shift by watching where the other competitor's spotters came up, he used Kentucky windage rather than sight settings to correct for it. And he was talking about Palma rifles with open sights. So, small moa numbers are discernible to the eye and, in the case of Tompkins, for one, even possible to correct hold for, though position and trigger control and equipment and ammunition that are all solid as a rock all have to be present for the shooter to be up to the task of getting the bullet where he wants it.