From what I gathered from (part of) the video, it's not about the HTML, it's the copy. Basically Google is accidentally/intentionally optimizing for copy that sounds like it came from an LLM or a LinkedIn lunatics post.

I'm skeptical but I don't have time to watch the entire video so I don't want to cast an initial judgement on if he's correct or if it just has to do with his specific copy.

It's not about the HTML. It's about the wording of the content. The more he had AI reword things, the better his ranking became.

google search evaluates based on their content and how they look. apparently, according to louis, AI generated websites get a higher score.