My curiosity piqued, I did a few minutes of detective work and figured out which cables are being referred to.
I notice that their higher-end digital cable (let's call it cable Z), which costs a bit more than four times as much as cable Y, has much higher capacitance, with slightly lower inductance (Ls = 1.5uH center pin; Cp = 270pf). That calculates to almost exactly 75 ohms!
It appears that cables X and Y, and possibly cable Z as well, use an unusual construction technique of having the conductive path for the center pin being a deposited layer surrounding a heavy gauge non-conductive core. The claimed advantages of that approach appear to essentially be mechanical in nature (durability and perhaps easier and more consistent manufacturing).
But I suspect that approach is the underlying reason for the relatively high inductance, which results in the cables having very high characteristic impedance unless the high inductance is offset by high capacitance (which is the case with cable Z).
The bottom line, imo, is that I would not recommend cables X and Y for use as digital interconnects.
Regards,
-- Al