LD4B installation on a 75 318

Screen Shot 2016-09-15 at 8.15.04 AM.png Thanks for the continuing follow up posts! I plan to look over my kickdown linkage as I am not getting a downshift at cruising speed.
One question I do have for you though is this:

Lastly, the kickdown MUST have a return spring on it. Not just on the carburetor, but also on the kickdown linkage itself to pull it ALL the way FORWARD when the gas pedal is released. Failure to have this spring installed can result in very hard shifting going into drive, reverse and second gear."

I have not seen this in the parts cars that I had, nor does it show up in the FSM illustration. I guess I have to ask why the kickdown rod has a slot in it if we basically want the rod to travel with the throttle linkage? Why not just a rod with a hole in it?
C