Yeah, this technique has been around for a very long time. I remember seeing an article in a Finescale Modeler magazine back in the early to mid- ninties where I guy was using superglue to cast teeth for a velociraptor model he was sculpting. I'll admit though that I haven't seen anyone trying to sculpt anything of this volume before. I'm sure it's quite expensive, but then again, for someone who doesn't cast things often and doesn't want to invest in more legitimate casting supplies for a small, one-of project, I suppose there's merit.
I agree with Paulson though, these days, there are better options. The thing that would seem to be problematic to me is that those kneaded erasers would probably easily deform while you're trying to remove the original object. Maybe they address that in the explanation, but I only looked at the pictures from the link you posted.