If you pay for Workspace (like he says he does) your data is your own, just like for any SaaS product.

I think it's reasonable to doubt this, and/or wonder how long until they decide to change this, and/or make exceptions like "to make your search experience better, Gemini now indexes your metadata (but only metadata so that's okay)"

Not really though. The data is also Google's and being in the US it's also accessible to other entities.

Then how is Gemini of any use?