Another look at directionality in cables

A friend of mine and myself were discussing this subject. It was brought up, if a cable is directional, why would both arrows on the positive and negative point the same direction. It appeared that, for example, that the positive would point from the amp to the speaker and the negative should point from the speaker to the amp ( even though there is no positive and negative using AC-reference only for phasing). This way, since the signal alternates, that at least the signal would be going back and forth on the wire in the same direction at any given time(maybe.) I have discussed with engineers about wire and most agree that it does have a (marginally better at best) flow in one direction depending on frequency and wire structure. All agreed it was not significant.
My friend tried it and said he got better results with one wire going one way and the other reversed---go figure. Of course with some wire, you do not have this option with it.
Opinions?