On a more serious note, I've been watching IPv6 "rolling out" since 2004 (which is when I had an active role in mobile network planning), and I'm somewhat saddened that we haven't yet been able to switch over completely (even if it is somewhat more awkward to shout IPv6 addresses across the room, which was one of the arguments one of my colleagues had against it.)
To clarify those of you who haven't worked in a telco core: You can't rely on DNS to configure core network gear. EVERYTHING of consequence is done using IP addresses, DNS is a convenience/comfort service for outer layers and end users.
The question is whether or not the /16 (of which most of the advertised/withdrawn /24s make up) was used by actual devices, or if it's address space NTT has yet to use. If it is assigned to NTT but unused space, then effectively no harm done. If it's actually used IP space, then that would be very inappropriate.