Take a look at this .... you are missing the trick....
With the Thrust Bearings the spring is allowed to move around the shock in a circular motion as its oscillating up and down....So the collar acts as a locater for the helper spring and the Spring.... but it also hides the thrust bearing that the main spring is sitting on and allows circular movement as it moves thru it's travel
This does two things.... it keeps the spring from binding up as it moves thru it's travel in all directions.....
And it allows you to make height adjustments easily by just using your hands to turn the spring up or down as you need 1 or 2 turns at the track to get more temperture in a particular tire..