There's limits to how far you can go with this — not only do humans make mistakes with this, but even in the abstract theoretical it can never be perfect: https://en.wikipedia.org/wiki/Münchhausen_trilemma — but it is still the "how".
(I wonder if giving an LLM content with intent to cause its users to spend money they didn't need to, would count as fraud, hacking, both, something else entirely?)
... the article did give me a different impression.
It's been found that data that begin with "Wikipedia:" are automatically weighted higher by language models during training, completely unsupervised.
https://www.bbc.com/news/technology-28481876.amp
https://www.bbc.com/news/technology-58559412.amp
(With apologies for amp links)