They aren't arguing against LLMs
They are arguing against their toaster's LLM to make the perfect toast from being trained on the tax policies of the Chang Dynasty.
As I understand it, the general ability to reason is what the models get out of "being trained on the tax policies of the Chang Dynasty", and we haven't really figured out a better way to do so than to throw most everything at them. And even if all you do is make toast, you still need some intelligence.
No you don't. That was the point of the example.