The rebooking hierarchy is listed
2.USE BOOKING CLASS HIERARCHY WHEN REPLACING FARES FOR FLOWN FARE COMPONENTS. THE HIERARCHY IS ECONOMY CLASS - Y B H K M L W V G S N Q O BUSINESS CLASS - J D I C FIRST CLASS - F A P 3
I agree it is obscure, but it is there; depending on how much hardball AA chooses to play, they can defend their position. As for a court, not a clue how they would rule.