I believe that the spring under the steering wheel imparts preload on the steering mast bearing. Without it, there will be play in the steering shaft when you pull up on the steering wheel.
Wouldn't the two angle ball bearings on top and bottom of the worm hold the play in the steering shaft to a minimum? With those adjusted to no play, there would be no need for the spring under the steering wheel. I don't recall removing a spring from the underside of my steering wheel, but I'd have to look at my parts stash to be sure.
