I'm not actively going out looking for other direct marketing companies in order to give them my data -- why would I do so with Google?
"This ad is based on emails from your mailbox and information from your Google account. Ads Settings puts you in control of the ads you see."
So clearly they are using your Gmail information for marketing purposes. Are they selling it directly? No. But it seems dishonest to me to claim that they aren't selling it just because there is a middleman (Google) between the marketer and Gmail user.
Google is different in this regard. Since they don't sell raw data, it's easier to opt-out (remove data via the Dashboard[1], delete your account, etc.).