Then either both conductors are in one cable or he didn't measure loop inductance.
It's easy to get confused between wire and loop inductance. A flat wire has much lower wire inductance than a round wire of the same cross-section area, that's why flat wires are better for 'ground' wires. But for loudspeaker cables, the closer the two conductors are to each other the lower the loop inductance. In effect the conductors cancel some of the wire inductance of the other conductor. The lower the inductance the better the high frequency response.
The electrical properties of a ribbon conductor are not the same as those of a round wire. A wide ribbon can be seen to behave similarly to a litz conductor where thousands of adjacent conductors cancel each other’s inductance. An extremely low Q circuit results with negligible roll-off. Given that there are four ribbons in each cable assembly, the effect is multiplied.
4 Ribbons connect to one terminal. The aggregate gauge is around 0. If your model were correct, then the cable should function as a crossover component and the roll off would be anywhere between 796 and 3183 Hz depending on the impedance of the speaker. This is, of course, not the case. I invite you to come and audition a system outfitted with this cable when you are in the S.F. Bay Area.
Nordost uses a similar approach and have 0.125μH/ft inductance. Plus/minus conductors are adjacent but are in a flat (litz like) arrangement to minimize skin effect and do not rely on side by side +/- round wire configuration for reduction in loop inductance. Oh and they certainly do not roll off highs.
In the Nordost loudspeaker cables, the Plus & Minus conductors are permanently molded close to each other (looking at the closest strands). So they may have reasonable loop inductance (I'll have to find the old equation book).