You will not get a EUA processed by the computers but you are still eligible for the upgrade at the gate when the GA processes the final numbers. Similar to star_world I have been cleared into F on flights where I was taking the free standby option for an earlier flight.

The trick is that the GAs have to process you into Y first, and then put you on the list for the gate upgrade. If the Y seat only opens up for you because of an upgrade then you won't get it. If there are plenty of Y seats they will likely process you into Y somewaht earlier and then process the upgrade list. You can check the PDA site once you're on standby to see your location on the lists and confirm that you've been added appropriately.