This is actually discussed in the interview: https://www.dwarkesh.com/i/176425744/llm-cognitive-deficits

It seems to be more nuanced than what people have assumed. The best I can summarize it as is that he was doing rather non-standard things that confused the LLMs which have been trained on vast amounts of very standard code and hence kept defaulting to those assumptions.

Maybe a rough analogy is that he was trying to "code golf" this repo while LLMs kept trying to write "enterprise" code because that is overwhelmingly what they have been trained on.