They said that about the glassbox engine too for Simcity, because apparently no computer could handle the mindbogglingly complex simulation going on at server level. Remember, what is infeasible one moment, suddenly becomes feasible when money and customer goodwill is on the line. Frankly I'd prefer a procedurally generated 50 mil stars with random planet, belt and station generation along with random seeded missions and whatnot that can be readily run on a local computer over all of this, and I know with absolute certainty that such could be managed on a local system.
Again, I don't buy it, and I don't think people should be so quick to buy it either. The whole "richness of the galaxy" ultimately is a smokescreen, when in reality a lot of it is effectively generated over a single seed and the main reason they don't want to deal with people using an offline mode is because then people would generate their own seeds and thus there would be different galaxies in existence. They want control, centralisation, and to be able to curate the content. They also rather handily put DRM in by the back door by doing so, because as a result you have to play on THEIR galaxy, not YOURS.