Teflon insulation is thinner than the common PVC, with the added bonus that it is more tolerant than PVC in surviving high heat. The Hall wires will not generate heat, but the phase wires can get very hot, and the Hall wires will be pressed up against them, so...the thinner Hall wires cannot dissipate and heat-sink the heat away as fast as the fatter Phase wires, leading to PVC insulation failure...
I use 24ga, but you can easily go thinner. I can send you a foot's worth if it will help you see if 24ga with Teflon would fit your application.