Thanks, I looked at some of those examples. Several I saw were suspiciously similar, and I wonder how they got that way. Others didn't look suspicious to me.
I wonder whether the similar ones were the result of something innocent, like a shared writing prompt within the workshop both writers were in, or maybe from a group exercise of working on each others' drafts.
Or I suppose some could be the result of a questionable practice, of copying passages of someone else's work for "inspiration", and rewriting them. And maybe sometimes not rewriting a passage enough.
(Aside relevance to HN professions: In software development, we are starting to see many people do worse than copy&revise a passage plagiarism. Not even rewriting the text copy&pasted from an LLM, but simply putting our names on it internally, and company copyrights on it publicly. And the LLM is arguably just laundering open source code, albeit often with more obfuscation than a human copier would do.)
But for a lot of the examples of evidence of plagiarism in that document, I didn't immediately see why that passage was suspect. Fiction writing I've seen is heavily full of tropes and even idiomatic turns of phrase.
Also, many stories are formulaic, and readers know that and even seek it out. So the high-powered business woman goes back to her small town origins for the holidays, has second-chance romance with man in a henley shirt, and she decides to stay and open a bakery. Sprinkle with an assortment of standard subgenre trope details, and serve. You might do very original writing within that framework, but to someone who'd only ever seen two examples of that story, and didn't know the subgenre convention, it might look like one writer totally ripped off the other.