[dotnet00]

15 was likely a pessimistic assessment. Likely calculated assuming that they have to use a regular old Starship (rather than a tanker variant) with near current specs, with no weight savings or any of the engine improvements, with conservative return fuel requirements. Basically, based on the data they had at the point of months before they submitted the proposal, when they were at the first iteration of Raptor and prior to all the different refinements they've been working on.

That said, that many launches is not that crazy and Starship wasn't the only proposal involving several launches and several orbital docking maneuvers. Basically all of them involved that in some form.

We've kind of been living in a bubble where any research on orbital refueling was forbidden by decree of Congress critters. But dozens of refueling launches should be well within our technical capabilities and SpaceX hasn't been the first one to suggest such systems. It's a necessary technology for realistically expanding human presence into space.