I'm guessing he didn't have access to any LLMs while competing, but I think a "centaur" approach probably would have outperformed both "only human" and "only LLM" competitors.

Reading through the challenge, there's a lot of data modelling and test harness writing and ideating that an LLM could knock out fairly quickly, but would take even a competitive coder some time to write (even if just limited by typing speed).

That'd give the human more time to experiment with different approaches and test incremental improvements.