It’s just one knob. Both the pressure in the window and the altimeter hands move when you twist the knob. On the ground you can set to the field altitude or set the baraometric pressure to what atc reports. It would be a good idea to set to the reported pressure and then check that the field elevation agrees. All in all vertical separation near the airport would probably be more accurate if everybody used the tower’s “altimeter setting” which is the local barometric pressure corrected to MSL. Altitude over terrain might be more accurate using the field elevation but the chopper pilots probably have radar altimeter and eveballs.
You too know what the hell you are talking about! I’m just a mere aviation buff since about 1944 when I got my first airplane ride.