I think Chevynut's comments on the length of the bushing and sleeve are pretty much what's going on.

If the maker of the pu bushing just mimics the rubber bushing it's not going to do the job very well. If you want a bushing setup that's free to rotate, the Delrin/aluminum bushings may make more sense for a lot of applications.

I have seen the shaft end bolt work loose on a tubular control that had poly bushings. But those were not even close to the style of stock bushings. There didn't seem to be much that could be done other than Loctite and torque.