Yes, exactly. But even the sub 5 MWe microreactors that are often shown in those truck demos require lots of shielding that has to be done on-site beforehand.
So you figured out this glaring hole in their plans that all the idiot companies doing SMRs missed?
Maybe not.
For example, Aalo Atomics has split the construction process in such a way that the on-site pour that happens after the reactor is delivered from the factory is (a) very simple (b) standardized, and (c) non-nuclear. In addition, the site work that is required is very repetitive, so you get a positive learning curve, again without the slowness of nuclear construction.
Copenhagen Atomics has heavy thorium salt shielding inside the nuclear core and a "Cocoon" that is delivered in 12 prefab parts installed on a regular concrete pad. So on-site construction is making the non-nuclear concrete pad, installing the pre-fab cocoon on pad and then placing the reactor core inside the Cocoon.
Westinghouse apparently ships the entire eVinci microreactor pre-assembled with shielding.
