Can't shunt to ground with passive guitar pickups, the pots need to have many hundreds of KOhms. Typical passive pickups pots are 500K. If you shunt this with say a 100K resistor, you'd be dropping the value seen by the pickup to <100K, and then you'll lose the high end.
While the standard audio guitar pots are "OK" for the volume control, they are wholly inadequate for the tone control circuitry, as I recently found out. On the tone control it all happens between 0 and 4, with the range between 5-10 being inconsequential. That is where adherence to the true power function would provide a more gradual tone response.