This might be to do with the fact that you appear on the manifest (and passbook BP) as AA EXP.

My one and only op-up was after boarding, on AA LAX-LAS, the guy next to me got really really tetchy that he wasn't opped up, the CC member turned to him and said "sir, this gentleman is an Executive Platinum cardholder, which means his a** is in an AA plane seat for over 100k miles a year, it's only right we thank him for his loyalty". Off I went up front, embarrassed to say I was actually BA gold.