The 'bug' of Luna appearing as a moon of Venus has been reported a few times. This actually working as intended
, although I may change it.
Because Earth has a population it is shown in the list of populations that precede the list of uncolonised bodies. As Earth is missing from the uncolonised list, the Moon follows Venus. I could include all the Moons of populated worlds in the populations list (when Moons is checked as an option) but I am concerned that would be more confusing than the current situation.
Steve