Of course cars wouldn't lead to more horses, because horses were the thing being replaced. But cars sure as hell lead to a lot more drivers, which is more akin to the analogy.

To take a software engineer for an example, Jevon's paradox would say that since software engineering is now so much easier due to LLM's, the demand will increase due to the reduced cost, which will lead to more software needing created, which paradoxically leads to more software engineers. There's no equivalent of the "horse" in the analogy, because the same people who were coding before ("driving" the horse) will be aided by LLM's in the future ("driving" a car.)