A chess scoresheet sometimes contains mistakes but chess players can figure out in many cases what was meant by thinking of what moves make sense and considering the level of play so far. Popular AIs tools fail at that.
[1] parrotchess.com, no longer available. Previous discussions: https://hn.algolia.com/?q=parrotchess.com
I think the theory is that the LLM having a high chess ELO was a pet project of a researcher that left.
explanation*. I must have been quite caffeine-deprived when I typed that.