You are free to not use it. You are not free to use the API provided specifically for the product, which you are not explicitly paying for, for a different product.

You can of course use OpenCode or any other project with the API, which is also offered as a separate product. People just don't want to do that because it's not subsidized, ie. more expensive. But the entire reason it's subsidized is that Anthropic can use the data to improve their product.

Do you not understand that they run the regular subscription at a huge loss? In exchange they require you to stick with Claude Code.

You are free to use the API.