Halloween Mia

So... I personally haven’t played Radient Dawn or Path of Radience, but every hero alt we’ve had has been next to their original unit... besides Sanaki but that’s an age difference. Both Mia and her Halloween alt shown seem to come from both Path of Radience and Radient Dawn, and they are both voices by the exact same person. Can anyone explain?
P. S. I don’t have a Mia but she’s next to Oscar.