It controls weight transfer front to rear under acceleration.
It controls how much the rear arm compresses on it's own under acceleration before it's coupled with the front & no more weight transfer takes place.
The longer the rod is extended, to more "free play" so to speak is in the rear arm to transfer weight before coupling takes place, & the shorter the rod, obviously the less takes place.
I personally have almost zero transfer set into our Apex & Vector. Just enough to get the front end light under hard acceleration, but not enough to pick the skis up. Wheelies are cool, but kinda tough to steer when off the ground.
Also, less transfer keeps the front end planted & makes for a great handling trail sled.
And yes, it would/should slide freely.