........... Banyan Bay shut down at 9pm every time,...........
More than likely due to the nature of Banyan Bay. Beautiful & quiet location with no onsite activities in the evening to generate any noise.
Having spent years on the island at differing times of the year, I do not know of any resort/condotel/condo dev where it is rowdy/noisy late into the evening, with the possible exception of Canuck's. And even then, define "late".
Additionally, most resorts/condos with pools shut them down by 9.