It doesn't need to, IPv6 has unique local addresses which is are non-globally reachable; I recall those had it's own can of worms depending on deployment but it's an option for private, local addresses.
EDIT: I also understood the GP comment to be getting around the problem of long IPv6 addresses and not actually making every machine globally accessible.
EDIT: I also understood the GP comment to be getting around the problem of long IPv6 addresses and not actually making every machine globally accessible.