talking about direction on alternating current makes as much sense as wondering how fast a rock can run.
the signal is fluctuating all the time, the magnetic field is fluctuating all the time, so how would a direction get forced onto the dielectric anyway? so we don't even have to wonder if it would matter, the idea is bogus from the start.
and cable burn in overall, is like burn in for everything in audio, things go from not good, to great for a reason that is beyond any natural law of physic.
things tend to go from good to not so good when left alone in the real world. I don't grow younger, the house doesn't fix itself. that's the real world. you can explain it with decay, with entropy or whatever you like, it's just a reality.
yes some systems have a period where things kind of "settle in" like car engine where you may not get the very best performance right out of the factory. but there are known reasons for that, the piston rings where made with a certain precision and the friction from running the engine will slightly reshape some parts to fit in better, or whatever I'm not really a car expert and I don't really know the english words. it's measured, explained, accepted. but even then they don't go "the paint will look right after 200hours, the air inside the tires will get direction, so avoid going in reverse for a few weeks". because they would rather BS you on making you believe that your D got bigger thanks to the car you're buying, than try to pretend the car will level up, evolve or burn in after 400hours.
now for a cable, it's hard to sell it by telling us that all the girls in the block will fall for us if we have that one cable. so the marketing guys have to get creative for once instead of relying on sex. sadly marketing guys are usually not the ones with the best understanding of a product or the science behind it.
still, for cables or an electronic devices, did you ever see your computer guy at the store come and tell you to run the CPU underclocked for 400hours for burn in? did you hear him tell you about cable direction changing the quality of the signal or how you should clearly get the the power transformer with the silver wire? how we shouldn't expect a game to run perfectly until the capacitors burn in and the bits get used to being in the hard drive? how we should extract all of the files in the game because the graphics aren't as good when it comes from .rar stuff that loaded textures at the start of the map?
of course not, we're not idiots we wouldn't care for that crap!
but take the same electronic, sell it to audiophiles, and wow! now everything is affecting everything audibly, and we must wait 400 hours even for the power ON button to burn in so that the sound really becomes alive and the soundstage opens up. are we audiophiles, dumber than the rest of the world, that we give in to those stuff and even care? or is it just that we're frustrated to see how now even cheap stuff sound transparent so that we need excuses to pretend that we're better than those other guys. that thanks to "know how" and money we still somehow got the sound that they don't even understand. "I don't want my music to be the same as what poor people have!"
when you get a new pair of glasses, the guy will tell you "oh you may need a few weeks to get used to wearing them", but he wouldn't add "because they need to burn in, else the colors won't be as vibrant and the field of vision will open up after 600hours". it's a given that we are the part getting used to it. and it's the human that adapts.
it's really an audiophile thing, to blame our own changes in perception onto the product itself. because most audiophile never ever question themselves, never change opinion, are never wrong, can ear stuff that cannot be measured and a lot of other superman fantasies. "science is not enough to explain how much of an amazing guy I am! "
me when I use something and don't like it, then 2 weeks later, I use it and find it ok, I call that "changing my mind". it's not amazing, it's not worth bragging about on headfi, but that's still what happened.