But why would wire benefit from a polarizing voltage? Yes, there is a capacitance associated with any interconnect, but that capacitance is minor in audio terms and it does need to "form."
One thought is that polarizing voltage allows the wire to work in a single-ended fashion. Maybe the molecules within the wire resent a reverse in voltage potential, a hysteresis effect of sorts much like that of the permeable metal in the core of an output transformer, which tends to sticks to one polarity and then the other. By placing a polarizing voltage between wires, makes the audio signal ride on top of the 9 volt potential. For example, a 2 volts input signal will appear on the hot lead as a sine wave cresting up to 11 volts and bottoming down to 7 volts, but never swinging negative relative to the ground lead.
The analogy that comes to mind is that of a Class A amplifier vs. a Class B amplifier. Without the polarizing voltage, the interconnect leads are like the output devices of a Class B amplifier in that in the absence of a signal they remain dormant, but with signal they become active. On the other hand, with the polarizing voltage, the interconnect leads are like the output devices of a Class A amplifier in that they remain constantly on.
I admit that this is a stretch, but maybe something like this is going on in most tube audio circuits in that the high-voltage, single-polarity power supply that is the norm and single-ended topology of most of circuitry combine to unintentionally polarize most of the components and allow only unidirectional current flow through these devices. Maybe all wires should carry some idle current?
How do we put these ideas to a test and without spending several hundred dollars? My thinking is that since the outputs of most tube line stages are capacitor coupled and many tube power amplifiers comprise an input coupling capacitor, it would take very little work to wire in a polarizing bias voltage for the interconnect.