Yeah, but there are voice actors that while able to change their tone, are really, unable to change their pitch much from their real voice. Then there are other VA's that DO have the ability to change their pitch, some quite drastically.
Even though Syaoran there sounds dead serious, the pitch of his voice hasn't changed. Vanitas' voice is, higher/different. He sounds more like Mamoru, but even then, as I said before, it's different. Considering that BBS comes out in just over 2 months, it wouldn't surprise me if Nomura coughs up all the Seiyuu's names by mid to late December, so I guess we'll all find out soon enough.