How confident are you that this knowledge was not part of the training data? Was there no stackoverflow questions/replies with it, no tech forum posts, private knowledge bases, etc?

Not trying to diminish its results, just one should always assume that LLMs have a rough memory on pretty much the whole of the internet/human knowledge. Google itself was very impressive back then in how it managed to dig out stuff interesting me (though it's no longer good at finding a single article with almost exact keywords...), and what makes LLMs especially great is that they combine that with some surface level transformation to make that information fit the current, particular need.