As far as I know, the rules at AK are the same as at the other three parks. Restaurants inside the parks take ADRs and walkups up to a certain time before the official park closing (I think it's 30 minutes). It takes an hour to clear the park out after closing, anyway, so if you're not done in the restaurant by closing, you still have time.
When you leave the restaurant, you will simply be another Guest that the CMs will steer gently toward the park entrance, just like those who sit down and take a nap right at park closing to avoid the crowds at the parking lot trams and park exits.