This is the interesting part of the experiment. Since these LLMs are general and not specifically trained on historical (and current) stock prices and (business) news stories, it isn't a measure of how good they could be today.
My first through after seeing this post was that it's a real world eval. We are running out of evals lately (arc-agi test, then sudden jump on frontier math, etc). So it's good to have such real world tests which show how far we are.