BITD cable designs were less well executed then what we have today. It was far more common to have cable friction/binding hinder cable movement. Der return springs tended to be heavier/stronger to over come this. Shift levers were also often more sloppy in their friction pack/lever movements. But since the cogs were farther apart then todays and the chains stiffer side to side all still worked well enough most of the time.

Push/pull cables with no return spring (when properly set up with no slack between the two cables) made for pretty reactive call and response. A nice feature given that the indexing was handled (bad pun) by the shifter end of the system (with the Shimano Positron version 1). (Much like the IHG 3 speeds). Andy.