Recently I was booked LAX-SAT-EWR departing at 11:55pm. I arrived to LAX in time to make the 11:15pm LAX-EWR. Because it was full, I couldn't SDC before arriving to the airport / going standby. At 10:48pm the check-in counter told me they couldn't put me on standby because the flight was under gate control, but that the GA could do it. I arrived to the gate at 10:54pm and asked to be added to the standby list. Despite having not cleared any standbys yet, the GA told me that she couldn't add me to the list inside of T-30 minutes. That felt bogus to me, but I didn't have a good argument / enough experience to fight it. 7 standbys ended up clearing and I'm confident I would have been on the flight if she put me on the list. Is that policy? If not policy, how would you approach having yourself added to the list given GA denial?
Appreciate any thoughts.