I think it just seems superficially attainable given things like 3-D printers and continuing improvements in AI, forget questions like how it fuels itself.
Yeah, we're talking about fully-automated, fully self-repairing facilities that encompass the entire vertical industrial production infrastructure - mining, refinement, raw material production, all the way to assembly of finished good and installation of those goods into the infrastructure.
We're not remotely close to having that on Earth, let alone as self-contained spacecraft.
