“Heinlein wrote FICTION.”
So did Jules Verne.
Your point being? As I recall Verne's moon expedition was shot from a giant cannon - a process which would have turned to paste any multicellular organism. As I remember he also had air and inhabitants on the moon. Are you claiming that Verne's/Heinlein's fictional plot devices are at some point in time going to turn into reality? Because if that's the case, then suddenly you're going to need a lunar atmosphere and lunar native inhabitants which is no more absurd than Heinlein's self sustaining lunar colony.
Edgar Rice Burroughs had John Carter on Mars with a breathable atmosphere and somewhat humanoid inhabitants. Does this mean that they're four armed Martian princesses?