AA and BA share revenue on TATL routes from the USA to the UK. BA charges outrageous fuel surcharges on award tickets; AA does not. Since the two airlines share revenue on these routes, it would make sense for BA to be the carrier to offer premium awards; that way, both carriers benefit financially from the fuel surcharge revenue.

Makes sense to me. I don't like it, but it makes sense. AA is in business to make money.
You can always claim an AAnytime award if you want to avoid the surcharges.