Today, the court found (among other things), that a few thousand of the summaries that Ross’s AI produced are way too similar to Westlaw’s summaries for it to be a coincidence.

This is probably just inevitable when your dataset is not large enough. I would be interested in seeing the LLM’s output and the original texts; I do remember the early ChatGPT producing some borderline copies of sentences that you could find online (with one or two words changed).