No I think in the age to which that camera belongs, if it is a 42mm thread, the automatic setting refers to the stopping down of the lens to the set aperture. In Pentacon/Pentax/universal thread bodies there would be a plate which pushed a pin on the lens causing it to close down to the set aperture. When you switched the meter on, the screen would go dark and the TTL meter would register. Full aperture metering used a second pin to tell the meter what aperture was set. Pentax, Pentacon and Fuji had different ways of doing this so they were only mildly compatible. Then they went to bayonet mounts. If your Exa is fairly old it may not have the pusher plate and the A/M setting is irrelevant.

David