Something weird is happening with LLMs and chess

I feel like the article neglects one obvious possibility: that OpenAI decided that chess was a benchmark worth "winning", special-cases chess within gpt-3.5-turbo-instruct, and then neglected to add that special-case to follow-up models since it wasn't generating sustained press coverage.

I suspect the same thing. Rather than LLMs “learning to play chess,” they “learnt” to recognise a chess game and hand over instructions to a chess engine. If that’s the case, I don’t feel impressed at all.

That's something completely different than what the OP suggests and would be a scandal if true (i.e. gpt-3.5-turbo-instruct actually using something else behind the scenes).