the section isn't even talking about Gmail users, it is specifically labeled for "Non-Gmail Plaintiffs". Google argues that:First of all,
The full quote that is being misinterpreted goes like this:
So, as you can see, the entire point is that automatic processing is such a "widely understood and accepted" practice that users are implied to consent to the practice each time they send an e-mail. This idea is called the "third-party doctrine" which holds "that knowingly revealing information to a third party relinquishes Fourth Amendment protection in that information". And, the quote which Google uses from Smith v. Maryland is a case which is often cited as the case in which the "third-party doctrine" was upheld.
The quote is a controversial one, as is the "third-party doctrine" in general. But, as of right now, that is the law. And, whether or not you agree with the law (and we would certainly understand those who don't agree with it), the fact stands that it is the law, and Google abides by it. It should also be remembered that the "third-party doctrine" is only being used to defend automatic processing, all of Google's other privacy policies still stand, so your e-mail is not shared with anyone unless you consent (or the NSA uses another questionable law to gain access).
source: The Verge