It's one of those policies that has never been enforceable - nor has anyone really tried to enforce it. Before the parks opened, when the resorts were open for about a week beforehand, you needed to show a valid reason to be at each resort. You still need to show a reason to enter the parking lot in your own vehicle or in a Lyft/Uber. But you don't need to show proof of a hotel or dining reservation to board any Disney bus, nor do you need to show proof at the door to the resort. No one asks people walking around if they have a valid reason to be there. Even when we've gone to resorts with an ADR, no one needed to see proof of it until we got the actual restaurant. So it's one of those things that is technically not allowed but no one bothers trying to stop it.