Fender Telecaster blender wiring - 15k resistor

[Don]

In Fender's original blender wiring scheme for the two pickup Esquire/Broadcaster/nocaster/early Telecaster, what is the purpose of the 15k resistor?

You can see this wiring scheme on page 63 of The Fender Telecaster (first printing) by A.R. Duchossoir.

[Don]

Apparently, it makes the dark switch position quieter than the other two.

I put a 22k ohm resistor between the switch and the capacitor and it makes the dark position sound like the tone control is down to about half rather than all the way.

It was still quieter than the other two positions so I put a jumper over the resistor and it became louder.

I guess the 15k ohm resistor lowers the volume like my 22k ohm resistor raises the tone control.