This. If you wanted the exit row, the appropriate thing to do was to ask the GA before boarding.

FAs jobs are not the same as GAs which are not the same as reservation agents which are not the same as tech support, Etc. An FA shouldn't be moving people into premium seats without payment unless there is an operational need to do so. Or is instructed to by the GA.

FAs aren't trained on elite benefits, and in most cases, don't need to be. Before departure, there could even be weight/balance considerations that come into play if you are moved to a seat that you aren't assigned to, and could put those calculations off. Not to mention, even if they do know about the E+ benefit, they likely have no idea if one who says they are elite are lying to get a freebie.

That said, I do understand why one would frustrated. But there is another side to this.