I get that, but from the tone of the conversation (Luke’s inflection and Yoda’s sigh), I have no problem interpreting that as Luke having asked the question before and Yoda having avoided answering it.
That’s a fair interpretation. I can almost get behind that, except, I just wouldn’t want to think of Yoda as being a complete ass about the topic (any more than he has been for hiding the truth to begin with). It’s obvious to him that Luke already “knows it to be true”, so with the Loth-cat clearly out of the bag, why drag it out any further?
Just for fun, though, I’m imagining the chat between them could’ve gone:
Luke: "No, Master Yoda, I will not levitate a single pebble until you tell me the truth. I must know."
Yoda: "Drop the subject, or back in the drink your ship will be.
😃