That's exactly the problem this modular type is supposed to address.
> small modular reactors (SMRs) are designed to be small enough to build in a factory before being shipped
> small modular reactors (SMRs) are designed to be small enough to build in a factory before being shipped
The AP1000, was supposed to address construction problems by being able to ship in large parts already constructed. But that failed so miserably that SMRs-long ignored because they weren't thought to be economically efficient-became the last ditch effort to build nuclear. And the AP1000 failed because of all the on-site mismanagement of things as simple as concrete pours.
SMRs are unproven in at least two regards: 1) ability to manufacture in a factory economically, and 2) ability to construct all the on-site infrastructure for the SMR to generate the electricity.
There are never certainties in anything except in hindsight. Most people with expertise who have reviewed SMR designs (and there are many) believe there's a high probability of the central manufacturing concept being able to work. Factories are a very well known concept at this point.
I'm a little confused by this, as all existing reactor designs required both the reactor and their infrastructure to be built on-site. I'm not sure why you think it would be an open question to just do the infrastructure.