Unless the fan is actually located IN the bedroom ... I don't see where the requirement for the AFCI exists. The code is pretty clear ... every "outlet" ... and a switch is not an outlet.
In a like manner, simply having the fan pull air from the bedroom does not place it 'in' the room. I suppose a bath fan, where the fan is directly mounted to a hole in the ceiling, could be considered 'in' the bedroom. Let there be even a foot of duct, though, and it's not in the bedroom.
Otherwise, I agree that the fan is likely in need of replacement.