>>539146978
The logical assumption is that they looked at the fact that a large section was just Lumine and Aether talking to each other and decided it made financial sense to trump big for both actors to voice out the scenes for both player iterations.
This is like 4 to 8 times more expensive than doing any other seen any other way but fans also respond to it very positively since it's... the whole point of the game? The knock-on effect is that since you've already hired them for that big section where they talk freely to each other, it's trivial to have them also do a bunch of lines for smaller scenes.
Still, I wish Lumine's internal narration to herself was voiced, it is in HSR.