Author here. In short, no, I wasn't surprised, I just wanted to cover it. I worked in 3D printing, albeit on the polymer side. On the metal side, there's been a lot of progress and 3D printed thruster nozzle assemblies are one of the key advancements SpaceX has made. It would never be a high volume process, but I was curious if you could get the kind of steel you needed for "surge" demand when the price matters less than total throughput.