It could very well make a molecular difference that simply isn't audible (thus not changing the sound of the cable). It's easy to get caught up in changes that very well may not be appreciable in the realm of audio. Surely putting Brilliant Pebbles all over the room would ostensibly would reduce resonance from audio waves. That may or may not actually do anything to change the way a rig sounds - but simply changing a physical property won't necessarily change the sound of the system.
BTW the food analogy doesn't work because evaporation is occuring. That's why food that's not properly defrosted will taste bad - the water evaporates as it melts and the food becomes dry and nasty (or freezerburn may happen, but that's a separate issue altogether from freezing and defrosting). In fact, proper defrosting (in the fridge overnight in a closed container) will yield food that tastes just fine. However, in the case of cables, there's nothing actually leaving the cable like there is when you defrost food. So the analogy doesn't apply directly.
The pebbles thing is a good analogy. You're not directly altering a rig, rather, you physically changing something, but everything is still the same. i.e. if you put all of the pebbles right in front of the speakers instead of just around the room. You didn't really change the sound of the rig, rather, you changed how the sound is transmitted...I dunno...I can't seem to convey it verbally. I have the picture in my head, but it's just not workin, lol.
But really, when you PHYSICALLY change the microstructure of something, although the final path of electrons is the same, the path in between point A and B changed so to speak. Kinda like taking a dirt road, but rather than staying on the beaten path, you stay a little to the left and it's not as worn down the SAME PATH so it's like a riding on an unbeaten one. Same applies to cryo treating something. It's the same item, just shifted a little. Wouldn't it yield a slightly different sound? just like riding down the same path a little to the left yielded a different physical affect.
I really have no idea whether it does or not. But I'm trying to wrap my head around how a physical microstructure of the same item changing, cannot have an adverse (positively or negatively) effect on the electrons traveling along that changed microstructure path.