Elon recently in an interview with Tim Dodd, said: "At SpaceX, we make the impossible late". In hindsight, nothing is impossible but before SpaceX did any of the routine things they do now, everyone said it was impossible: private company getting to orbit; landing rockets back on earth (let alone on a floating ship in the middle of the ocean); etc.

So if history is any lesson, when SpaceX makes a claim, one has to pay real good attention to details and question all their own assumptions hard because these guys have made impossible possible time and again.