official answer
Sales manager at MOW told me the following (he's a great friend of mine and i've known him for a long time, so it's official and accurate):
"For sure, cannot use facilities during platinum plus week"....that would be July 4th week.
also, he said they "reserve the right to limit use during ANY week that has near full occupancy, simply because the facilities are very busy, and the priority goes to the guests who are in current occupancy."
... that is reasonable!
Any other Marriott resort will say the same about limiting usage during busy weeks.....i.e., "they reserve the right"..... but in actual practice, they usually don't.