Is there any way for a user using the "Login with Google ... for individuals" auth method (I guess auth method 1) -- to opt-out of, and prevent, their input prompts, and output responses, from being used as training data?

From an initial parse of your linked tos-privacy.md doc, it seems like the answer is "no" -- but that seems bonkers to me, so I hope I'm misreading or misunderstanding something!