Clearly one travels in F because they want to travel in F.

The point is, with fares that can be $20K RT... 160K (which you can only find on a handful of flights throughout the year and usually close-in) you just have to do the math to make sense of using miles vs paying for a rev ticket. Idem for J. The delta is far, far less for Y. That's the reason why premium redemptions, particularly internationally are a better VALUE. That said, there are definitely people that don't know that (the majority), or don't care.

As for the theory of 800K being for heavily booked flights that isn't exactly how dynamic pricing works. There are algorithms in place which predict demand. It is that predicted demand which drives the rates quoted, combined with another component- AA's rev management team-- which will try to extract the highest price and then discount if their algorithm isn't correct (which is also why you see those 80K seats on JL "dumped" last minute) So you could have a flight with zero seats booked and still coming in at that 800K rate. AA has zero incentive to offer 80K on AA metal unless they know the seat is not going to be sold.

The worry here, if AA gets rid of fixed partner redemptions then the program is pretty worthless IMHO. It's most likely to happen where there are revenue sharing and fare coordination agreements in place. In those scenarios both airlines have closer understanding of demand -- and share information. The second most likely scenario is a hybrid one where there is an AA segment combined with a partner airline. There AA can play its shenanigans freely, as does Aeroplan.

Sadly expect those two scenarios to increasingly occur... oh the enhAAncements....