Just like how it is hard to fact-check Wikipedia now that it's used a reference. A thought came to me - perhaps it's Wikipedia that should be worried that it'll be supplanted by LLMs.
The phenomenon they're referring to is when something spurious is posted on Wikipedia with no or poor citations, then used as the source for a "reputable" article (without citations), then the article is cited by Wikipedia, making the spurious information look more trustworthy.