I think the claim is plausible. If you've ever watched Grand Designs, a lot of the houses (especially the cheaper or less traditional ones) use prefab pieces an

I think the claim is plausible. If you've ever watched Grand Designs, a lot of the houses (especially the cheaper or less traditional ones) use prefab pieces and are incredibly fast compared to traditional timber frames with poured concrete. In the last few seasons, in particular, a bunch of the houses use pre-built wall (and even floor) "cassettes", also called closed-panel frames, that come with everything from the factory -- not just structural framing, but layers of insulation, breather membrane, vapor barrier, etc., complete with inside-facing gypsum drywall -- and simply lock together. There are also lots of examples of custom off-site-engineered steel or wood pieces that are CNC-machined (almost always shipped from Germany or Switzerland), and also very fast to install, partly because they can machine them to a high precision. At the construction site, it's just assembly.