That's not what a coincidence is.
A coincidence is: "a remarkable concurrence of events or circumstances without apparent causal connection."
Are you saying that training it on a subset of specific data and it responding with that data "does not have a causal connection"> Do you know how statistical pattern matching works?
It's not coincidence that the answer contains the facts you want. That is a direct consequence of the question you asked and the training corpus.
But the answer containing facts/Truth is incidental from the LLMs point of view, in that the machine really does not care, nor even have any concept of whether it gave you the facts you asked for or just nice-sounding gibberish. The machine only wants to generate tokens, everything else is incidental. (To the core mechanism, that is. OpenAI and co obviously care a lot about quality and content of the output)
They are useful. It's not a coin flip as to whether Bolt will produce a new design of a medical intake form for me if I ask it to. It does. It doesn't randomly give me a design for a social media app, for instance.