They claim not to save your chats and not to use them for improving the AI model. Using GPT-3.5 Turbo through DuckDuckGo is definitely better than using your phone number to sign up for an OpenAI account, so yes, I think it makes sense to use this. But ideally, you could just run an AI model offline on your own hardware, I recently saw a Lemmy comment that explains this very well: https://lemmy.dbzer0.com/comment/10348570

You can also use @db0@lemmy.dbzer0.com’s AI Horde as explained here: https://lemmy.dbzer0.com/comment/9295041