That's kinda what they do. They release the older stuff for free once they have the newer things. Also duck.ai does a good job of anonymizing your prompts, so it is an OK investment, and the chats are stored only on the browser. Be sure to know how to properly wipe browser history to remove all traces of the chat you had if you want to be 100% private.
I use Venice.ai, which is another private anonymous LLM that only stores chats on browsers.