Well... no shit? If you gave someone permissions to read your emails, obviously they can read your emails. And because they can read it, they can also copy your emails and/or share it with other companies. This isn't something that can be stopped by google.

Ya, the entire process is only to vet companies' policies on data access, retention, etc.

https://support.google.com/cloud/answer/9110914

On an opt-in basis, which seems fine. A lot of people want email activity being fed to some other tool like CRM or call center software.