If you think about it, clay absorbs contaminants. They are somewhat on the surface of the clay for a short period of time. This can cause a little marring maybe, but clay is soft, so stuff can get "pushed into" it easier.
With this product, where do contaminants go? From what I understand it's a rubbery texture. Since it can be rinsed if you drop it, I'm guess particles are not absorbed, but sit on the surface. This means any sap, fallout, metal, or dirt it's removing is spinning under your DA, correct?
Also, since it needs to be "broken in" when brand new, I'd have to assume the material itself can scratch. You don't have to break in microfiber or foam pads when brand new, or clay for that matter. Maybe it's good for production detailers, but for my cars I'll stick to fine clay.