What's the point with that quite lackluster story in Endwalker?

[Garet]

Is there any reason why the unsundered world wouldn't have a moon? Was it even otherwise stated that the unsundered world doesn't have a moon?

The original unsundered world also had their own moon. The fourteen reflection (13 + our source world) are basically reflections of the original world that were sundered into 14 copies. Hydaelyn decided to imprison Zodiark on the source's moon while scattering his other fragements to the other reflections

[KizuyaKatogami]

The original unsundered world also had their own moon. The fourteen reflection (13 + our source world) are basically reflections of the original world that were sundered into 14 copies. Hydaelyn decided to imprison Zodiark on the source's moon while scattering his other fragements to the other reflections

This isn’t explicitly stated, in fact someone above already linked hydaelyn’s telling of the events which is that she supposedly created the moon to house Zodiark. Considering Elpis takes place before all that the moon shouldn’t be visible unless she was flat out lying.