Since your comment seems to be strongly contradicting the blog post, it might be worth checking whether you are really testing the same thing.
The blog post is about playing chess against GPT-4. GPT-4 (or at least, a version without image input capability) is available at https://chat.openai.com/, but only to "Plus subscribers" who pay for it.
So did you test with GPT-4, or did you test the "default GPT-3.5" model which is available for free?
And did you actually select GPT-4? It is shown at the top of the conversation page.
I'm asking because I noticed that the default setting for each new conversation is currently still GPT-3.5, even if you are a subscriber and even if you have selected GPT-4 for your previous conversation(s).
Come on. Yes. Here's a screenshot if it helps: https://i.imgur.com/BepKMt1.png - It gives FEN notation itself, so I prompted it with FEN, but I have also tried describing the position of each piece explicitly.
The blog post is about playing chess against GPT-4. GPT-4 (or at least, a version without image input capability) is available at https://chat.openai.com/, but only to "Plus subscribers" who pay for it.
So did you test with GPT-4, or did you test the "default GPT-3.5" model which is available for free?