> being disappointed that the Pro tier was opt-in to training on prompts by default

"Opt-in" means that the default is non-participation, for example, not training on your prompts. Is it possible that you intended to say "opt-out", which means that the default is participation? That's what the context seems to suggest.

See, for example, https://termly.io/resources/articles/opt-in-vs-opt-out/:

> Data privacy laws like the GDPR and CCPA give individuals the right to opt in or out of different data processing activities.

> · Opt in consent means the user takes an action to show they agree to something,

> · Opt out consent is when they take an action to say no.

Or https://bigid.com/blog/opt-in-vs-opt-out-consent/:

> • Opt-in consent requires users to actively agree before data collection or processing.

> • Opt-out consent allows data collection by default unless the user declines.

This is an important distinction, because confusing the two (as you seem to be doing) can lead you both into unethical fraud and legal liability.