I guess everyone has a different opinion.

I believe this is just for animals that compete in agility events, and I'm not sure they are even registered, I think it's just that they can compete. I personally disagree with the s/n requirement. What if someone wants to breed a dog for agility? Why not go to the ring?
On a similar note, I think the idea of what a dog show is has moved so far off its ostensible purpose that s/n'd dogs should be allowed to compete. Hey, maybe the animal has a sister.