Producing hallucinations or not isn't just a setting you can tweak in the model. The entire function of GPT-3 is to guess the next word from the words that came before. It's a hallucination machine that has been trained on so much real-world data and has such a large parameter set that for commonly known and discussed information it does a remarkably good job at creating factual sentences. But as soon as you get out into territory that it doesn't have memorized, it will do the next best thing and produce credible-sounding new material that may or may not be complete nonsense. Again, this isn't a setting you can tune, it's just what a transformer does. It models human language, not all of human cognition.
Also, since we can watch the model evaluation and see all its weights, there’s research that shows you can determine if any answer is a “retrieval” of existing knowledge or a hallucination.
I have read many similar comments to the grandparent, all saying the same thing, “I tried it, and it turned up wrong facts” all the while they forgot that they were deeply engaged with the content it was producing. Just think of how much our attention is monetized already, money will be poring into this space from here on. It’s only a matter of time.