This is my take as well. A human who learns, say, a Towers of Hanoi algorithm, will be able to apply it and use it next time without having to figure it out all over again. An LLM would probably get there eventually, but would have to do it all over again from scratch the next time. This makes it difficult combine lessons in new ways. Any new advancement relying on that foundational skill relies on, essentially, climbing the whole mountain from the ground.

I suppose the other side of it is that if you add what the model has figured out to the training set, it will always know it.