Not sure how much light this adds to anything, but the QF terms and conditions are based on eligible booking class, which for AA clearly state F, A and P will be awarded as First Class.

If you go to AA.com and select a first class fare (with restrictions), it gives you the YUPP, but it books into First. So the eligible booking class is A or P. You only travel in Y if A or P is not available. There seem to be some domestic flights where all you get is either 'full' First, or the option of YUPPs (for discount), I'm not sure how you could go about booking a discount First class fare other than by a YUPP.

Given that the YUPP is still double or tripple the discounted Y class fare, I don't see YUPPs as far as earning F class status as a 'loophole' or otherwise.

BTW - just having thought a bit more about this... awarding points / status credits on eligible booking class rather than fare basis works both ways for QF and other O/W programmes. For example, you book a AONE3/4/5 - but in Australia, or Europe where there is no First you fly Biz class - only getting Biz class points. If points were awarded on fare basis, then you would be given F class points as the ticket as a whole is in A class. Works the other way of course for DONEs, as you get to fly F!

Regards

WG