Per Missy's suggestion, I just called the Gold desk. I was told "whenever we request upgrades for tickets on American or any other carrier's ticket stock, we send a cancellation of the ticket to the other airline when we modify the record. So the only way you can get an upgrade when on another airline's ticket stock is to make your request on the day of departure".

I am not saying I buy this explanation (even though she did go away and ask someone else). I am simply reporting what I was told. This continues to be a can of worms IMO.

I am going to cancel my current res that is on hold.