The point of the example is that math does not just logically derive from observation of the natural world. The reason we, in modern times, might intuitively think otherwise is because it so beautifully describes much of the universe around us. Yet these descriptions, or even the possibility of their existence, are impossible to even begin to imagine until you have developed math itself. And the problems we might think of it as solving aren't really problems until it's invented. As the tribes show you don't even need the ability to perform basic counting to live and thrive as a people.
And yes, it's going to be a slow process. Human intelligence is not about speed. The capability to do simple arithmetic rapidly correlates with intelligence in humans, yet a calculator can perform said calculations many millions of times faster than the fastest human. Yet that of course doesn't mean said calculator is thus millions of times more intelligent. The question is how long would it take an LLM to discover mathematics starting from the same empty baseline? And, using current methods, the answer is quite simple: never.