I'd never heard of Carnation opening for breakfast before a couple months ago, so it may be a new thing (or just because we're usually there during off season with fewer crowds.) I do know the first reservation available during our October trip is lunch and not until 11:50am. If they are open for breakfast, the first reservations inside the park is usually 10 minutes after opening (based on my experience with the other inside area restaurants.)
You might call Dining to see what they say if no one here knows.