Google's privacy policy, effective Oct 16, now says it won't show personalized ads based on Drive, Gmail or Photos content "unless you choose to make data from these services available to other Google services that support personalized ads." The Oct 1 version had no exception. Google says ads won't be "based directly" on your inbox. Android Authority: disconnecting may not erase data already saved in Search Services History.
https://www.theverge.com/tech/1017600/google-personal-intelligence-privacy-policy-ads-update
The VergeNow Google says it might use your Gmail and Google Photos data to target adsAccording to the new terms, sharing your data for better AI recommendations also means opening it up for more personalized ads.