>>7738260>I'm pretty sure Arturia Lily was already known to be the younger version of Arturia well before F/GO was a thingAs someone who played Unlimited Codes on PS2 the very same day it was released, I can assure you that it was just a dress change in the actual game where it appeared first. And most probably added so they could make the Saber Lily figma to go with the exclusive edition (this was my first figma because I bought that edition mostly for the game, by the way).
There's nothing in-game there pointing at this being a younger Artoria other than that skin having Caliburn instead of Excalibur. Artoria had the exact same personality in the game, you can tell by how they drew the faces and also the two figma faceplates didn't show that naive expression that one could see in Grand Order. I guess they could have already thought of it as a younger Artoria and it could have been explained in supplementary materials, but it wasn't presented as that in the game at all. It was just a skin that didn't even have it's own story in the arcade mode.