Jevons paradox starts with some resource being used more efficiently.

A classic example could be coal. The first steam engines used a ton of coal, but over time more efficient steam engines where created that used way less coal.

One might think that this caused the global coal usage to go down. But the opposite happened, as the overall cost of doing something with a steam engine went down.

Note, that the price of coal itself can remain fixed in this example. So Jevons principle is not (directly) about a resource changing in value.

If LLMs make codes cheaper to produce, then obviously more code will be produced. That's not an instance of Jevons paradox even though the article claims so.

You could say that LLMs means that we can create software with less of the resource that is human software engineers. So one might think that we'll need less software engineers in the future. If, on the other hand, we end up needing more software engineers, then that'll be an instance of Jevons paradox. But the article is not making that claim.