Rebirth's battle director, Teruki Endo, confirms this to be the case, noting that, even though Sephiroth is only playable "in a limited area", the team still took the time to develop his moveset.

You won't at all be surprised to hear and see that one of the first cards shown off from the set features Sephiroth coming down from the heavens, sword in hand, ready to stab you-know-who just ...