I would send a note to AA asking for a refund, citing the T-45 check-in and ask that if AA can't make the refund that it document the T-60 ticketing deadline for you. Make sure that you ask for a refund as opposed to some customer service gesture.

The mere fact that others have been able to book later doesn't mean much. Same thing as excess weight in checked bags, size of cabin bags, change fees and the like. It's largely about the individual agent unless the terminal locks the agent out at T-60.