No it isn't. If you have a regulatory structure that makes progress so expensive and counter to the government plan then progress is very hard to make.

Even the regulatory agency themselves have realized this and are changing their structures.

> What has also prevented changes from happening is that nuclear scales down poorly, so the cost of iterating designs is so large.

US regulation allows nothing between fully commercial and university research making any time of prototyping impossible.

Its in fact very possible to make smaller reactors that can teach you a lot and are not absurdly expensive and still useful. That data then could be used for to further inform regulatory agencies.

> The replicated nature of these sources is an advantage in so many ways.

Yes but even if it doesn't scale down well in terms of engineering you can still do factory construction of reactors. If we can mass produce plans, rocket engines, rockets and cars then the same could be done with reactors.

The reality is the government selected one winner and made deploying anything else practically impossible. The change in regulatory agencies has basically made progress impossible beyond marginal improvements.