They do not clear the parks but they do enforce the No wristband, no ride, therefore most go ahead and leave.
Wristband Distribution Locations
Wristband for the evening EMH hours can be picked up at the following select locations in the theme park that is open for the Extra Magic hours.
Magic Kingdom
Main Entrance, Plaza Rose Garden, The Timekeeper, Seven Dwarfs Mine, Liberty Square Riverboat landing and Caribbean Plaza
Epcot
Main Entrance, Future World East Breezeway, Future World West Breezeway, International Gateway and Mexico Bridge
Disney-MGM Studios
Main Entrance, ABC TV Theater, and in the courtyard near Rock n Roller Coaster
Animal Kingdom
Main Entrance, Its Tough to be a Bug Fastpass location, Harambe School in Africa, Entrance to Asia and near the Boneyard