> Based on my understanding of the approach behind ChatGPT, it is probably very close to a local maximum in terms of intelligence
To me that is an open question. OpenAI has not revealed a lot of the relevant stats behind GPT-4. I also haven't seen anything about their future LLM research (though I haven't looked very hard), but I think the above assertion remains to be seen.
Some humans never learn this, and those that do could take years or even decades of training. AI's are learning some things much faster, though since their "brains" are not like those of humans there's no reason to expect them to learn in the same way.
No, but children spend years learning basic mechanics, how to navigate 3-dimensional space, what causality is, etc. Underneath these laws of nature you find… logic and mathematical relationships. So I don't think it's surprising that a model whose perception is restricted to text (and now single images) as the sole sensory input/output might need much more training and data to learn logical reasoning.