Yah. But did you miss their reference to "Re-Evaluating Satellite Solar Power Systems for Earth" by Geoffry A. Landis? Which in the context of their vision could imply much less heavy industy and mining for all of that stuff, instead doing it on the moon, where it doesn't matter. Massdriving it from there to whereever, thereby enabling beaming solar-power down to earth by micro-waves as a side-gig.

Off the cuff, so to speak?

Could even be made mandatory, as a sort of machine tax, and remediation for all the exhaust the starships will blow out. Same way as for ships and planes. Or make them fly with atmospherically sourced syn-fuels :-)