All very good players I'm sure, but average ain't everything...
You're def right there, if player A plays nothing but 18 hole RGs, and player B only played 9 holers, player B will have a much lower average if they are equal in skill. For example if A goes 27-30 for 57 in 500 straight 18 hole RGs, and player B shoots 500 27s and 500 30s player B will have an average of 54 and A will have an average of 57.
Now take player C who focuses on unlimited tournaments he could be far less skilled than the players that do mainly single play tournaments yet have a far lower average.
All in all, average is a pretty meaningless measure of skill.
edit - I do appreciate the time you spend on this genorb, and it is interesting to browse through the list.