Separately, the industry standard elsewhere appears to be that if you're a free user your data is used for training, and if you're a paying user it's not.
Permission to use your content
[...]
This license is for the limited purpose of:
[...]
- developing new technologies and services for Google consistent with these terms
The last item sounds like Google can use my content to train an LLM, no?> Your content is not used for any other customers. Your content is not human reviewed or used for Generative AI model training outside your domain without permission.
And I think the default assumption has to be that those policies are actually followed. If you think they aren't, the burden of proof is on you to show they aren't.
The amount of times Google has been caught out doing things they shouldn't be means that no, no one has to prove that it's a reasonable assumption that Google follows policies, not even their own.
It's for you to prove that they can be trusted (good luck with that!).