Not all resorts are created equal. The Oasis Pool (leisure pool) at Poly, for example, has MB scanners and access is restricted outside of open hours (which are 7am-11pm). Will they kick you out if you're in past 11pm? Not likely.... but you can't get in the gate past that point.
Same at WL, the leisure pool gates are also MB controlled.
Some resorts don't have MB scanners on their leisure pools. They all do have posted hours, whether you see them enforced is another question.