Then what was the point of Sora sealing them? o.o The way I understood it was that sealing a keyhole protected the heart of the world from the Heartless.
Well I just read the Ansem Reports again, and it seems I'm wrong on that matter. The heartless can sense the whereabouts of the keyhole--they can't do much of anything until it's open.
The keyholes weren't sealed--closed, but not locked in other words. Ansem Report 5 made that evident to me.
He might've opened it, and that's what brought about the world's destruction
He did.
Zexion mentioned he did, at least.