This is one of the causes there's a push to run your own engines for large language models: if you run your own service you can control the environment, data and reproducibility.
This is exactly what my employer is doing, they pay so that our internal data (from employee queries) does not become part of the model. They've blocked the public chat gpt etc.
openAI claims that user data is not being used for training since March 1st.
Only for the API. If you are using the chatGPT website, that is fair game.