That's the objection: The court order requires them to retain everything they currently have, even if the user requests that it be deleted.

Because the New York Times sued them and made them.

https://openai.com/index/response-to-nyt-data-demands/

ChatGPT (the app) specifically says they keep deleted conversations for up to 30 days. That's probably why.

yeah but the link states "The 20 million user conversations were randomly sampled from Dec. 2022 to Nov. 2024" so this makes no sense. 2024 was much longer than 30 days ago

Because the court ordered them to retain the records longer than they normally would.