I have and use a Cryo'd Squeezebox. I have cryo'd breakers, romex, and outlets in my sound room. I have no way to A/B compare the stuff in my walls. However, I have compared cryo'd and non-cryo'd tubes, SB3, and some equipment power cables.
It made a noticeable difference in the tubes - 1 became defective due to the cryo process, and was clearly very different than before... it made weird sounds on its own, and then none.
I think with the SB3, it made an internal component stop working sooner than a non-cryo'd unit.
So, it really tests the gear and will expose any weakness.
With just plain cables, my guess is the effect on the insulation will likely offset/add/change the overall impact of the actual changes to the crystalline structure of the metal that changes.
If the cable manufacturer had the raw copper cryo'd then insulated it, that would make the most sense. But that's me, a layman. Could be that insulation is OK to super-freeze and then thaw without any negative impact... I don't know.
I do know that cryo'ing does change the molecular structure of metal. They do it to barrels of guns and that helps with accuracy... The electricity should flow more efficiently but whether that's a good thing or not would require a comparison.
The process costs money and is generally lauded in the audio community which is why the guy thinks it adds value. But hardly anyone has compared a non-cryo'd to cryo'd speaker cable in reality.