So they use a different AWG with the bi-wire option? The William Tell zero is 13 awg.
Most Audioquest speaker wire are comprised of 4 wires for RED+ and 4 wires for BLACK- (the low end products such as Rocket 33 use 3 wires or 2 wires for each RED/BLACK). When they do the bi-wire on a speaker cable, they just take 2 wires for each banana/spade connection. The core 13awg speaker wire is the same. You just are splitting the speaker wire "in half" for bi-wire option.
If Audioquest really doubled up on the bi-wire option, the price of the "bi-wire" version would be over TWICE the price of the normal version.