Thank you to tom911 & benmaller for answering this - the only thing that I would add is that the Diamond welcome amenity point will have to be requested (and many CS agents will say you don't get it because they don't know how to do it - it needs to be posted separately) - so I would not stress over how the stays post (as GP points or AA miles) just call after you've completed a bunch (might as well be all 5) and ask them to convert the GP points stays to AA miles (and to ensure that you get the Diamond amenity also). You're not entitled to any Gx points though.