I'm not so sure that Time Traveler is correct.
We recently purchased an EOY odd Marriott Grand Chateau week via resale. The closing process took much longer than I expected. When I asked the escrow agent why, she told me that the seller had elected points for 2021 prior to the sale and that Marriott would not let the deal proceed until those points were returned (thereby clearing 2021 usage for us).
My advice: ask Marriott.