or is the advance just that the sled itself is now on preloaded ball bearings.
Ie all piccies i have seen still show the focus knob "appears" to push the mirror sled via a tangent bar as per current mechanisms. The ball bearings mean a tight fit with no friction for the sled, hence no mirror slop, but it still seems to be just a bog std offset dual speed focusser mechanism driving it all???.
That would be a correct assessment to the best of my knowledge.