AAV vent in attic

Looking at a house in Michigan. Bathroom was remodeled with an added tub and walk in shower. It appears the tub has its own vent line with an AAV in attic. AAV is about 8” above insulation in attic. The main vent is about 15” away and looks original. My handyman says an AAV for one fixture is fine as long as there is still a main vent out the roof.

Is an AAV in attic a concern? Code issue?