As the music signal is always on alternating current and its wave shape is virtually symmetrical above and below zero, the movement of electrons has to be equal in both directions in a cable, and also drain equally to earth. But if a cable offered less impedance in one direction, distortion of the wave shape would be caused by partial rectification the conversion of alternating current into direct current. I have never seen a technical explanation offered in support of directionality in cables.
Superstition is rife in hi-fi circles.
Listening evaluations have proved more effective than sophisticated measurements, so subjectivity is considered respectable. However, at the source of the music, recording and radio studios use great lengths of cheap non-directional cable for analogue signals, seemingly without degrading the sound. But if this does damage the sound, there is nothing that the listener can do about it. Yes, certain hi-fi loudspeaker cables are directional but not necessarily in multistrand and interconnect cables. This directional phenomenon seems to be related to the physical distortion induced when the copper for the wire is drawn down to its diameter from its original ingot and specifically to the last direction of pass in this multistaged, wire drawing process.