Looks like the top hat can expand and contract independently of whatever spring is under it so it's almost like threading the perch up and down on adjustable height coilovers on the fly. I would suspect you set the ride as low as you want it for normal driving, since the target audience is for lowriders with speedbump woes, and then pneumatically expand the top hat temporarily to clear something, then lower it back to the bottom so that the system is unloaded most of the time.
There's nothing wrong with riding on air all the time as long as it's built strong enough for that, however it would dampen the springs some, plus you'd hate to have the pump running constantly it there's a tiny leak down. Even if it's a pneumatically operated hydraulic ram with a lockout, there will still inevitably be some leak down, but at least it wouldn't be compressible like a purely pneumatic ram would.