Some of the measurement schematics are stolen from others. They got it wrong. Mr. Townshend copied the mistakes.
He ends up with C- capacitance.
Capacitance is defined between two points. If the speaker cable is a joint of the black and red wires, tubed in a plastic encapsulation, there might be some capacitance. Get two separates, no more any capacitance.
What's the big deal?
But loosing the capacitance will not change much the muddy bass, the unclean mid and highs. Getting a cable with a low resistance ref. to DF will. Garantied.