I think the response to you then was correct ("This is a common "gotcha" comment from people who don't understand LLMs very well. Occasionally if you ask Gemini it'll say this as well. It has everything to do with the fact that ChatGPT is the most talked about AI model rather than data being trained on it").

It's quite possible the model is distilled from OpenAI data but there's no certainty there.

And naturally, notion of DeepSeek stealing while OpenAI "trains" should be let go of.