I think it's very likely. This is the reason why I stay on GitHub Copilot business for the time being as a solo developer. I assume that Microsoft has less incentive than Antrophic to break the business agreement and use data for training or re-sell it to Antrophic. If I was using the heavily discounted subscription plan from Antrophic, I would 100% assume everything is fed to the machine. I'd rather pay whatever the API costs, than give it an exact recipe to build my product.