Some
might get away with it, but there's a risk.
From the AAdvantage Terms and Conditions
(link)
Earning AAdvantage Miles
"You cannot accrue partner airline miles with your partner frequent flyer number if you have already used your AAdvantage number to obtain AAdvantage program benefits such as First or Business Class upgrades, baggage fee waivers or complimentary access to Preferred/Main Cabin Extra seats. Additionally, you cannot redeem partner airline miles with your partner frequent flyer number and obtain AAdvantage program benefits such as priority boarding and access to preferred seats."