I just had this happen. Wife and I flying LAX-JFK-ATH on one ticket and daughter flying JFK-ATH on a different ticket. Wife and I on SWU, Daughter on mileages upgrade. I have EXPL, no one else has status. My daughter got upgraded and there was one SWU seat still showing available. AA said that the seats were released one at a time so my wife and I didn’t get the seats even though there were 2 seats available. I probably could have split us and given her one seat but I didn’t do that. Seems crappy that the person with no status gets the upgrade over someone with ExPl.