[superbirds]

Yes it does have air bags and height valves - after thinking about the pressure affecting the height - you're right that just doesn't make sense if the height control valves are working and adjusted.
If I understand there function, they are a simple centering valve with 3 settings - release - neutral - pressure - determined by the arm attached to the axle. The overall system air pressure should make no difference as long as the valves are working.

Thanks Richard for getting me on the right path. I'm in way too many rabbit holes.