Not sure it's a justified reduction in exclusion zone. Yes they use natural circulation to get rid of decay heat if they lose power to run the pumps. BUT - they can't tolerate multiple reactors failing at once, they can't tolerate more than a few control rod withdrawals, and they can't tolerate clogging of the flow channels - Which to me, seem like reasonable accidents. The reduction in exclusion zone for NuScale is not really justified. If they get a reduction, you can expect the big ass reactors to also get a reduction...
I don't really have an opinion on the matter and I think it's a fair question to consider, but I'll note that the NRC obviously disagrees. At least for now, they could always change their mind. I seriously doubt that they would ever significantly reduce the exclusion zone requirement for any of the currently operating reactors, however.
