DuoPars had a very strong return spring. So if you used one with SunTour BarCons you had to tighten the shifter so much that it moved very stiffly. This, combined with the tight spacing of SunTour Ultra 6 and 7 freewheels made for poor shifting. Offsetting the cable anchorages reduced cable tension so you could adjust the shifters to be buttery smooth. And also increased lever travel between gears which worked well with narrow spaced cogs.

BTW I also sold several inner plates with the 2nd idler wheel attached, well before the introduction of the SunTour LePree. Great for wrapping up chain for ultra wide ratio setups.