I've been booking while logged into my AS account for years without any problem getting AA credit. That way I don't have to enter my passenger info each time. The only thing I have to do is change my FFN during the booking process. I can track all my upcoming reservations on my account (even if crediting to another FFP), and if I cancel a paid reservation I can have the funds go to my AS Wallet.

IME, it won't recognize AA status until immediately after ticketing, so you have to go back into the reservation to select a PC seat, if desired.