FWIW.... had an OC5 tied to a reservation. Travel plans completely changed and now trying to apply it to a NC4 Starwood hotel. Still can't attach them. Nice lady on the Marriott Reservations line and is very helpful but the issue is on the Starwood side and they apparently have no idea how the certs work on the Starwood side. The Marriott lady flat out said that they have no idea when they will able to use these certificates.
They can book with points now but not with certs. Absolutely no ETA. Hope that Sept ~17 deadline will fix things.