Right, he still has access to his Google account, but he can't use YouTube from that account. In fact, he can't create a new account and login to YouTube from any of his devices. His only access to YouTube at this point seems to be through non-logged in access.
You can still track users without accounts. It's called finger printing. It's still probably associated with the main Google account too. There's tons of articles on Facebook and "dark" accounts.
