> Welding for high stress, corrosive, high vibration, high heat and high safety requirements is extremely difficult and highly skilled labour. And rightly so.

I didn't say anything to contrary. I am saying that car factories can churn out high quality welds at scale, but construction companies can't.

> Regarding house building, there is only so much that can be pre-produced. Assembly is still on site, and that will always require rework, nobody can afford the site preparation and parts manufacture at the required tolerance levels to avoid that.

Compare https://en.wikipedia.org/wiki/Manufactured_housing

It looks like 'only so much' can go pretty far.

I think you are unaware of what has been achieved for years already in Europe by companies like Haus - https://haus.tech/, Huf Haus, and Hanse Haus. Assembly of an entire house in 1-2 weeks implies little or no rework.