You can opt out of training.
If you don't believe checking the opt-out box actually opts you out, then this sentence could be said about literally any provider.
Maybe I am biased, but the person in control of that specific company is by far the most untrustworthy.
All providers are equally trustworthy :)
Yes but grok has the literal track record of our of the box uploading your whole codebase, secrets included to a remote box.