I'm can't watch these videos, but there's thousands of 1–2.5mm$ homes being built west of Austin, Tx (who's buying them!? I DON'T KNOW!)

I like ti watch these houses go up: the walls & roof trusses are all laminate and come in to the job site in segments. It's takes a crew of 2–4 (depending on the size of the house) about 4 days to assemble the exterior.

The interior is about 50% 'modular', and the rest is traditionally framed. It's pretty insane.

Pre fabricated assemblies exist all over but are highly constraining if standardized or need to be custom ordered to fit which becomes expensive. You still have to assemble and seal everything on site so you don't necessarily save anything and it limits you in other ways. Building wall assemblies isn't the hard or expensive part of construction.