Well, it's not so much about "how much" reflection, but "what kind" of reflection. The light frequencies that are returned by a DVD and a mass-produced CD are different than the frequencies returned by a CD-R. I don't think there are any CD-R's whose spectrum will work on a DVD player. CD-RWs just happen to fall into the range that the DVD laser needs, but that's more of a coincidence than a deliberate design choice.