It would be helpful if there was a consistent policy with UG's but this is one area where it is difficult.

At the DO, it was made clear that the policy is if you board, you lose your spot on the UG list. The reason is GA's are under great pressure to get the planes out on time and in most cases, there is simply not enough time to search for whomever was next on the list.

But that is not always the case. Sometimes there is sufficient time and it is GA discretion to notify the FA which pax already boarded who can be moved up. Obviously this happens a lot.

If the policy was only that if you board, the UG is lost could mean the aircraft goes out with empty F seats. No one wants that. It would be nice if DL could come out with some alternative published policy in the event there are empty F seats but I wouldn't count on it. Just as a data point, I have seen only a couple instances this year where there was an empty seat in F at pushback.