I use it all day at my job now. Ironically, on a specialization more likely to overfit.

It may be a statistical model, but ultimately nothing prevents that model from overfitting, i.e. memoizing its training data.

This seems to imply that not only did entire books accidentally get downloaded, slip past the automated copyright checker, but that it happened so often that the AI saw the same so many times it overwhelmed other content and baked, without error and at great opportunity cost, an entire book into it. And that it was rewarded for doing so.