You should watch the videos I gave you that show them using same assets, locations from PS3 code.
It's called transitional period.
Your previous comment sounded like they built everything from scratch with Luminous, which is not the case. They were able to use some of the code, models, and assets, then when Luminous was fully built transition those PS3 assets over and revamp them with new DX11 api.
To say they didn't reuse character models and the battle system is absurd. They did while the fully built and added the new engine, then transitioned work flow fully to luminous.
You don't scrap years of work from one engine to remake animations for characters. You export them setup the new engine to accommodate them, then add to them. Some engines allow you to import raw polygon files that are not even out of box modeling into a completly different engine environment. Then let the engine do some of the vertex/vertices mapping and tessellation to give you more detail in your character models that was not feasible in previous engine because of hardware limitations.
My answer still stand they re-used a lot from their work when it was Xiii versus. A lot of the prototyping was kept, and even enemies. You don't thrown away years of animations, rigging, and designs when the characters/story for the most part are not changing.
