I think (and hope) you will find that the CMs try to be a lot more diligent about checking for wristbands during the special party nights. From what I understand, they have been pretty good at removing those without wristbands before the party stuff gets going. If someone remains in the parks during an evening EMH, they can't go on the rides, but that's about it if they don't have a wristband. I doubt if a CM would say anthing to them if they saw them buying something in a store. But, during a hard ticketed event, I believe the CMs will stop anyone they see without a wristband since that person would be able to watch, for free, a parade/fireworks/stageshows that others had paid specifically to see. I believe they make announcements before the official closing, then CMs start 'sweeping' those non-party goers toward the front of the park at park closing time.
Since we have't heard anything to the contrary so far, I can only assume it has been working. I truly believe that we would have heard if it had become an issue since there were so many people that were concerned about Disney's ability to clear the park of non-wristbanded people.