As I understand Jane Street they have done great things for OCaml and they also do their own web framework (I guess that big money bin needs a lot of dashboards).

I think the designer here takes a wrong approach and sort of falls into engineer envy where he wants to make prototypes as deep and realistic as possible. And that is not really the most important part of the design job.

The most important thing is that the right thing gets build (why do we need a JSQL input box? what do we actually want? what are other ways to do this?). And this is often better done with pen and paper sketches, meetings, observation, discussions ... rather than too quickly narrowing on a particular design and spinning into discussions on whether buttons should be on the left or on the right, LLM intricacies etc.