That stuff is kept separate from all account data (like with Google DNS[0] and fonts[1], too): no common cookies, "unauthenticated" (ie. no cross-referencing with Google accounts), logs retain no referrers
I don't read it as stating that the data is kept entirely separate. In fact it references the general privacy policy making it quite clear that whatever data is collected is governed by the same rules as everything else.
What's the meaning of the data being kept separate when these databases could be linked with minimal effort (e.g. via IP addresses), for examples at the request of law enforcement (US or other).