Look, people. They redid the lip motions on all scenes where the lips actually moved.
This isn't a separate piece of data. It's included in the entire scene. To have lip motions matching japanese and english voices, they'd have to have two scenes.
Plus, you forget the FMVs. Those would most certainly have to be duplicates, even if the others weren't. Square doesn't want to go with a duel-layer disc(For reasons of cost and cheapassness), so it's not gonna happen.