There's billions of years of compressed knowledge in those 4 year olds. Lots of useful priors.
Also language is a fairly recent development in human evolution (only 60-70 generations ago) which makes it much more puzzling how a mechanism that is so efficient and effective could evolve so quickly, let alone pondering how actual languages evolved (almost instantly all over the world) given how hard it is to construct an artificial one.
More like 1000+ considering the Chauvet painters certainly had speech.
I don't see GPT's blunders as mistakes. They are to us for sure but would not be to another GPT instance in that it would produce the same continuation to a prompt and thus agree.
We have no idea how evolution "readied" a deeply complex organ like the brain over many thousands of years, then almost instantly repurposed it for language acquisition and generation. To further hypothesise that what it was "readying" was something that trains from data in a way similar to how chatgpt is trained from data makes it even more astonishing and until this is demonstrated it is more scientific to not accept this hypothesis.
That ChatGPT is capable of producing human-like sentences from pattern recognition without any universal grammar baked in, even if the underlying reasoning might be flawed, goes against the argument of something such as universal grammar existing.
At the very least, it shows that a neural net is capable of parsing and producing coherent grammar without any assistance from universal grammar. It does not prove that humans don't have it, but it does make a compelling case that it's clearly not required for humans to have it either.
You didn't address or missed the main point: chatgpt requires something in the order of a trillion tokens to be capable of producing what you mentioned in one language.
There are 40 months old babies that are fairly conversant in both Chinese and English, and are able to detect sarcasm with something like 0.0000001% of the tokens, doesn't that give you pause that part of language acquisition is innate to humans and is not entirely acquired the way chatgpt is taught?