Wow, this is news to me, and a great feature I should take more advantage of if it indeed is permissible. I had always been under the impression that most deeply discounted fares domestically (maybe just 48 US, but possibly 50 or all of N.A.) specifically stated any stop greater than 4 hours was a stopover, regardless of whether you did the last in first out trick. I know that CO applied this rule quite regularly, hence why I never even thought to try it on AA.