When you go to the Gemini in Chrome section on the same privacy page it states:
'When you use the Gemini in Chrome feature, Gemini collects and processes page content and the URL from the browser tab you’re viewing by default. Some of the page content Gemini uses might not be visible to you."
I think they're being reasonably explicit about what they're doing.
Note: I'm in the EU so not sure if this is what's shown everywhere else.
It's right there in the privacy center. The answer is quite unambiguously yes by the way. (This is for the Gemini app):
"How your data is used
Google uses this data, as described in our Privacy Policy, to:
Provide our services
Maintain and improve our services
Develop new services
Personalise our services (learn more)
Customise our services
Communicate with you
Measure performance
Protect Google, our users and the public
These uses extend to the generative AI models and other machine-learning technologies powering our services."