The AA site is glitchy. If you see the QR space on BA.com, you can most likely book it through AA, but you should call. If the AA website errors when booking, it ties up that inventory for some time on an incomplete PNR floating out there in the ether, so if availability is limited, don’t try online first because if it fails then there won’t be any left for a phone agent to grab when you call. But just in the last week I have booked 4 different J awards on QR metal using AA miles.