Okay I can guess the answer to this.. But really why does the ridges make it illegal? They aren't really significant. I don’t think they would help the disc stick in the chains that much. You could look at some of the soft discs and they are probably stick in the basket better.
I think it is a great disc to putt with. I started turbo putting before I seen anyone doing it. It worked for me. When I seen this disc I thought it was the coolest disc that I have seen since the first Z plastic discs. Could the reason be that it gives people that turbo putt to much of an advantage in the putt itself as far as accuracy and distance?