Demo and pilot plants tend to be small because they are intended to prove the technology to be feasible and economic. The next step would be a commercial scale plant.

Wouldn't more small reactors be better for management of power production? If one of 20 needs maintenance, you still have the other 19 to supply consumers with electricity.

While if you need to power down a huge reactor for maintenance, its backup must be of the same huge capacity.

I think the point is that the reactor modules are small enough to transport by truck.

It's a demonstration plant. Testing small proof of concept first, I guess.