It doesn't have a concept of not knowing. You can literally type gibberish like "goronne domkiry awerquin mernacb" and it will produce matching output.
Did you try? It replies "I'm sorry, but I don't recognize the language or the words you've written. Could you please provide more context or information about the language or the origin of these words? That would help me understand better and provide a more accurate response."
You must be using gpt-3.5-turbo, try it with text-davinci-003. They did... something to 3.5 beyond just RLHF and it's somewhat lobotomized now or strongly biased towards producing canned output for prompts that aren't middle of the road.
