Perhaps so, but surely the FA would know that the seat is now occupied by a FAM. So, the passenger could explain that he was removed from that seat to accommodate the FAM (who HAD to be given that particular seat under FAA regs). The passenger, who likely selected his seat months in advance in order to be assured of first pick of the entrees, shouldn't be disadvantaged simply because AA had to comply with federal law.

I'm sure the FA would be very understanding.

I do the above on the infrequent occasion when a couple asks me to move so both can sit together. I always am willing to do so (for couples, NOT for business associates). But my one condition is that the FA take my meal order to reflect the priority of my original seat assignment. Usually, the FA just takes it right then and there. Sometimes, she/he comes to my new seat right after takeoff.