^assumption
My ass, especially when the whole game clearly stated that Dinopolis was stolen from it's dimension by the entity to counteract Chronopolis. That is newton's third law that with every action, there's an equal and opposite reaction. And quite clearly, im using it as an analogy.
Answer: As a result of the time clash, the dimensions split. The point in
time where Chronopolis and Dinopolis was hurled to, another moon came in
existence.
Answer: Harle is indeed the moon. There are two moons in this world. There's
another moon that exists as a sibling to the bigger moon. And Harle is a
fragment of that smaller moon. Her name itself is [tsuku-yomi] (meaning moon-
reading), hence she has plenty of lines with "to the moon." Well, certainly
Harle existing as an opposition to Kid had been established in the beginning,
there were also many other parts with this meaning.
There are discreprecencies here that are not answered. So ofcourse, this is an inference.
Masato says that the moon came into existence, but does not say that the moon came from Dinopolis. Thats one.
Two, the moon is different to the other moon. If the moon was indeed from Dinopolis, the moons would be the same. Unless their moon was bombarded by meteors, or magical, it would not appear red and nor would it be a different shape. Remember, the Reptite Dimension and the CT dimension are timelines that split off around the prehistoric era, where there was a possibility of a difference. Something like Lavos was a major time influencer, just like Serge, who had the power to shape the future. His shaping of the future allowed the humans to excel.
Now, Masato says that Harle is a part of the moon. And that the new moon is a sibling of the other. Now, the sky dragon is represented by the big moon. Harle is the dark moon. Hence, Masato may have used this to say that she was the sibling. Harle's existance quite possibly created that moon. Harle herself didn't need to exist at the time if the moon was created after the time crash. Remember, what Harle is - that is a part of the Dragon God which is the incarnation of all elements. So simply, Harle herself split off from the Dragon God, and retained that element, whatever the dark moon may be.
End of Inference/ non baseless assuption.