Yes, for speaker cables, it's just for reference. At least that's what I've been told by one great manufacturer and a couple of dealers whom I consider to be very knowledgeable. So, I suggest doing what is most convenient. I have heard speaker cables not sound their best for a day or two if their direction is reversed.
Interconnects seem to be a different story for the reason I described above. Although -- Siltech believes the opposite from what I described! I have reversed the direction of my Siltechs and can tell no difference whatever (after they settle in again). The main thing seems to be that, in I/C's whose shield is separate from the signal conductors, the shield is grounded at one end, not both. But even that directivity may not be a big deal.
Larry
So is it belief or do you take it as fact? I ask because you say you have heard a difference regarding speaker cables.