That's for shipping... shipping does undo burn-in for some cables and especially ribbons. 24 hours often isn't long enough, I'd say 3 days as long as the cable has been thoroughly burned-in previously.
When comparing cables, if you handle them gently, preferably just removing the plugs and leaving the cables where they are, it is possible to do valid comparisons.
This goes for all cables though, it's just a matter of degree. Silver and teflon used in any kind of cable and even capacitors, generates static charged when handled, but it's possible to recognize that and listen past it. This called the triboelectric effect and when the charge effects the signal it's triboelectric noise. Because of triboelectric noise, with very sensitive multimeters you often have to let the leads settle for an hour or more to get a correct reading after hooking them up to whatever is being tested, what a huge PITA!
What's interesting is round wire cables, even silver and teflon, after they have been shipped and re-burned in a few times, finally settle down and the effects of handling are reduced to insignificance. I think this is due mechanical stresses in the dielectric from being coiled onto a spool and uncoiled. Naim actually built a machine that shakes their cables to mechanically destress them, I think it also requires several sessions of destressing with electrical burn-in in between the mechanical destressing. This process may reduce burn-in to insignificance, but it would cost a lot. I'm not sure this is 100% possible with ribbon cables due simply to their shape and the fact the dielectric will move vs the conductor when bent, generating more charge.
There is no doubt evaluation of any kind of audio component or system change can take a lot of thought, effort and time to perform properly. It's easy to attribute a change in sound to an incorrect cause as the system's behavior is often more complex than we give it credit for, so there are unknown unknowns that confound us.