If BA have to start paying/compensating properly then they’ll just starting downgrading people or IDB. It may be cheaper in the long run. And I’m not suggesting OP would be the one getting booted out of First. More likely someone on a 2-4-1 or cheap A fare where the cost to BA is potentially negligible.

I’m not sure if this has been asked, but I do wonder whether OP paid for an AUP into a seat that shouldn’t have been sold. Maybe a checkin agent missed a note - not entirely sure how it works on FLY.