although I can't prove it, I suspect that this lens modifies the shape of the aperture blades, or the opening, somehow.
My own pet theory of why preset lenses have better bokeh than modern lenses is a combination of round apertures at all openings, (due to any wher from 12 to 18 sculpted blades) as opposed to hexagonal, pentagonal , etc openings as a result of straight (or nearly so) blades. That plus position make presets have better bokeh.
Now, apply that to nikon's lens. what if (Someone please confirm this or refute it) the bokeh control changes the shape of the aperture, (rounder or straight sides), and moves it longitudinally to maintain correct aperture as well. Does that achieve much of the same benefit?
great for speculation over a drink or two. Hell it took almost that to make me think this idea up in the first place