Nobody was scammed. 9.3 was given as a preliminary BR based on the aircrafts flight performance. Nowhere was it ever said or advertised its BR would never be changed.
It was too powerful for 9.3 in game due to its armament mostly, thus has been moved up to 9.7.
All vehicles are subject to a BR change at any stage to balance the game. That on top of players feedback requesting a rise to 9.7 / 10:
You indeed do, you paid for a Harrier GR.1 and you still have your GR.1. At no point anywhere is it said, advertised or been even mentioned that premium vehicles cannot have their BRs changed.
All vehicles are subject to BR changes.