There is no way a top 100 course is remotely as busy as an average course. Nearly all are private, and a typical private club has probably 30% of a typical nearby daily fee course. Many are destination courses, limiting play even more, and most are pretty exclusive, also cutting down on play.
The NGF estimates that there were 465,000,000 rounds played in the US, and there are 15,000 courses in the US, so an average of 31,000 per course. If the average top 100 club plays 15,000 rounds, that works out to be 0.3% of the total US rounds.