And, quite a few courses are only available as 9-shotters, CTTH and such, starting with the first of the named famous courses, Pebble Beach.
Perhaps this statement answers the Q behind your Q:
No, there aren't any courses hidden for beginners and whatnots - all available courses are available from day one.
There are 13 genuine full 18 holes courses (*), 11 free + 2 suject to a fee
(+ 5 "Best of" track selections),
there are 9-shotters available from these courses, frequently two of them,
there are 11 more genuine courses available (**) ONLY as 9-shotters, + 3 "Best of" selections.
(*) including Bandon, a selection from one golf resort
(**) sometimes 2 selections: Pebble, Hilversum
P.S. *giggles* because of another proof concerning the lack of QA:
Their on-site ads still state "21 famous courses..." while there are 13+11