Originally Posted by flyingmonkie

My understanding is that if it's passed T-72 then theoretical seating will have started to kick in which can do weird and wonderful things with blocking seats so it might be that.

Or, it might be another passenger with status moving their selection around.

I doubt it's deliberate because that would require BA's IT to have identified you as somebody who wants to book a pair of seats and then shown you a specific seat map... far too clever by half!