I have never seen this . . . . . the braid cover for UV protection? Or does it also have some other function? If it is mostly UV protection, I would imagine a tightly braided dacron cover would also work (for less money and more likely to be in a scrap pile for most people).If you thread the shock cord down thru the middle of a piece of dyneema single braid, it can last a lot longer.
good durability testing is really hard to do and there is relatively little data on what works and why. So crowd-sourced ideas, where the better ones get good word of mouth diffuse out more widely to more people than the worst ones . . . .seems the way this works in practice.