The human brain doesn't even have the concept of written language, that's all culturally learned knowledge.
If you have no answer, I put it to you that your assertion is of the no-true-Scotsman type -- that is, unfalsifiable.
The impossibility of testing whether the brain is adequately simulated (since a pretty basic LLM that makes no attempt to simulate the functions of a human mind yields human-like text i/o) is a point in favour of it being unlikely that we could design a fully functioning simulation of a human mind out of arbitrary material(1), since the inadequacy of testing is an impediment to actually building it.
(1) it's apparently possible for us to create human minds out of bits of humans and a process called pregnancy
Its not the no true Scotsman fallacy unless the Scotsman actually exists.
So it's literally the inverse of "no true Scotsman". We don't have Scotsmen not doing things that all "true Scotsmen" are supposed to do, we have "definitely not Scotsmen" passing benchmarks for Scottishness (in a world in which Scotland itself is only an aspiration)
In my first comment, I didn't claim that it's simulating the entire human brain but aspects of it like language and memory.
We can test such aspects by throwing text at the model and comparing it to responses of humans. A simulation doesn't need to have the same abstractions. What counts is solely the quality of the response. If the responses are sufficiently close to those of humans, I'd say it's simulating a human brain.
We happen to know how LLMs are trained, and from the loss function it's pretty clear that blood sugar will not magically enter the equation, nor even motor neurons, except as abstract knowledge that the model can reason about.
A LLM trained on western texts will, best-case, simulate a western abstract reasoning process, which usually puts more focus on independent/isolated explanations compared to other cultures. From that training data it will not spontaneously start simulating a generic human brain that was separated from both its cultural knowledge and its spinal cord.
At least in the same sense that the Mandelbrot fractal does not contain a picture of the maxwell equations. You may actually find that picture, but by looking hard enough in a complex enough system, you can find just about anything else you want.
We can with reasonable certainty say that there are still significant differences between LLMs and human brains, but this notion that we can say with any certainty that similar structures won't form as a side effect of sufficient training is pure fiction.