That assumes you trust Google and many people don't. The fines companies face for violations are peanuts and there may be real incentives internally to using this data. "Accidents" happen after all in complex data systems and they're already allowed to mix the data for "security and abuse". On that note, as I read it, closing all your Google accounts as a result of suspected abuse due to DNS data would be fine under the policy.
First is whether you can trust it, second yes, their privacy states that they don't log IP, and frankly with dynamic IP it isn't really that much valuable anyway. The other information together can tie that to you as a person. Combined with other information that you are disclosing when using their services (since their policy changed many years ago, to allow sharing data between their services) they know exactly who you are and what you're doing on the net.
I really don't understand why those DNS services are so popular. All you need is list of 13 root DNS servers[1] (you only need one, but 13 for resiliency) and a recursive resolver and you can run your own caching server.