That's from the 90's, actually: but that doesn't apply to whole sentences of creative text. The true genius of "natural language" now rears its head...I should have been more clear. The onus would be on the content creator using the material to report it. DM's Guild could then impose sanctions/penalties for failure to comply.
Back to the original discussion..
I wouldn't be surprised if he wins. If I am not mistaken, wasn't it fairly recently that publishers were handed a defeat in court in that they couldn't copyright game systems?