UA's new system of selling upgrades out from under their elites, while claiming to do otherwise, is one of the biggest reasons many of us have jumped ship to AA. It would indeed be quite troubling to discover that AA is moving in the same direction and would possibly cause their recent efforts to recruit us to backfire.
Since AA seems to be much more responsive to public opinion than UA, this is the time for us to make a lot of noise and make it clear to them that it's a bad idea to mess with the upgrade system like this. That said, I have no problem at all with AA selling upgrades for seats that really would have otherwise remained empty. In fact I've already been surprised to see some empty F seats on a recent flight, which I haven't seen at UA in several years.