The voltage readings are not reliant on the length of the linkage. The switch does not know how long the linkage is, it only knows when it is under tension or compression.
The voltage readings are a function of the system. Forward mounted controls at rest, no pressure on the lever, the switch is sending 2.6v to the ECU. When you put upward pressure on the lever, the switch is under tension and sends 3.6v to ECU. Down shift, switch under compression, 1.6v to ECU.
When moving pedal assembly to the forward position, adding the linkage extension keeps the lever position in the same orientation to the pedal. If you adjust the linkage to be longer the lever will be further up, so guys with big boots can get their toes under.
I have adjusted the linkage length on my rear brake lever, by two full rotations, to raise the lever to a position that I find comfortable.
I will add that I am new to Rockets and have not yet had a close look at the quick shift assembly, but it is a basic mechanical function. And here's my joke. It's not Rocket Science. lol.