I follow what the QRH says but its a doubt I'd like to clear.
Good thought! I've had a few guys over the years leave it in "Auto" only to have a few ATC units (Bangkok and Hong Kong come to mind) remind us the set it to "On," rightfully so, per their airport requirements (Ground Radar, etc). So, it would seem that in "Auto" with the aircraft on the ground (Airbus), it reverts to "Stby".