I'm confident they don't want your code in their training data. The amount they have to lose if they're found to be using customer code as training data is enormous. Plus there are no guarantees that your code is good for training a model - model providers have been focusing much more heavily on quantity rather than quality of training data recently.

(Worrying that they may log your data and then have a security breach is a different matter - that's a reasonable concern, they've had security bugs in the past.)

I call this the AI trust crisis: people absolutely won't believe AI companies that say they won't train on their data: https://simonwillison.net/2023/Dec/14/ai-trust-crisis/