You're right, the website should contain a more explicit note that user data is subject to OpenAI data retention policies. (However, I do mention that "Your data is never recorded, and opted out of future model training according with OpenAI API policies"). OpenAI did change their policies recently, and opted out any API data from future model training and promised us they delete it within 30 days. I wouldn't call it false advertising, but note taken, users must be explicitly told that their data is sent to OpenAI.
The claim that "Your data is never recorded" may even be legally fraudulent. I'm glad that you don't record the data, but OpenAI does - making the claim as written a lie.
I understand why you made these decisions, but the website should not contain borderline false advertising.