User asks for recommendation. AI generates answer saying product is absolute garbage. Company pays to simply have that portion of the answer just not appear. It will be a post-filter sentiment analysis on the original answer. Nobody can ever prove what would have appeared or not.
This is the beauty of AI - while a search engine is at least semi deterministic and you can reasonably question why it wouldn't bring up a site that is clearly relevant, AI has plausible deniability. who can ever say why it generates this answer or that?