> Even mentioning usage of differential privacy for a single feature of Gmail seems pointless to me when they obviously not only have everyone's emails in full history, but also develop countless algorithms to scrape content from emails (e.g. purchase history from common retailers).

That's an unsubstantiated claim, and I don't think that it can be in any way reconciled with Google's own privacy policies.

https://blog.google/products/gmail/g-suite-gains-traction-in...