My take away from that discussion was that “the dark of the moon” is itself a mystical thing that is distinct from “there isn’t moonlight”; when the moon is in the sky, but there’s no light reflecting on it, it mystically interacts with the curse. This doesn’t make scientific sense, but these aren’t scientific werewolves.
edit And in fact, I believe the point C&A were making early in that discussion is that it has to work that way in order to have both a situation in which a moonless night prevents werewolves, and the ability for werewolves to shapeshift underground or indoors where there is no moonlight.
If you’re in space and there is no moon at all, what’s happening is that all the parts of the werewolf curse that interact with moonlight are returning a mystical “divide by 0” error, so all that’s left is your general ability to shift.
(Can’t speak for the size of moons part; it’s possible that only the number matters for the curse, not how big they are, and a world with two moons of very different sizes would have each have the same impact on a werewolf.)