It looks like Figure 1 shows some sort of an IMD test, perhaps demonstrating that frequencies higher than 20kHz can intermodulate and produce difference frequencies in the audio bandwidth. This is a real issue in active circuits. But not in cables per se.Okay, maybe this was clutching at straws, up at these silly high all but rf frequencies as all the differences that could be shown
However, poor RF shielding in cables can admit RF into the signal path, where they can potentially get demodulated into audible artifacts. If Stereophile were interested, they could test cables for RFI. But they're not.