Genuinely curious, where does google actually use differential privacy?

Chrome telemetry is one example I know of: https://www.chromium.org/developers/design-documents/rappor

Very related to differential privacy: https://research.googleblog.com/2015/08/the-reusable-holdout... (together with IBM and Samsung)

Can you quote specifically where they said they were the only ones doing it?

I watched that presentation and I don't recall them claiming to be the only ones using differential privacy.

Which is why I used "paint", not "said". Not that I expect a company to explicitly say in their big day that others were already doing it, of course.

But my impression from the presentation, as someone who had never heard of differential privacy before, was that this was brand new research from some professor, which they contracted to help them apply it to the real world. Definitely not "this is a technology that's used to achieve such and such, this is how it works".