Yes, they are checking to see everyone has a room key.
We had a situation this weekend in the DLH E-ticket with a family brought in all their friends. I know this because the dad specifically said when asked "Do they care if you bring all of us in", "No, no one checks the keys. I always just book 1 room, then everyone comes over to eat..." They brought in about 12-14 of their closest friends. They cleaned out the breakfast area before I could get pics on Saturday, so I had to take pics Sunday morning.