That's not what Jevons paradox means though. He's just name dropping some concept.

Jevons paradox would be if despite software becoming cheaper to produce the total spend on producing software would increase because the increase in production outruns the savings

Jevons paradox applies when demand is very elastic, i.e. small changes in price cause large changes in quantity demanded. It's a property of the market.

> Agents, by making it easiest to write code, means there will be a lot more software.

He's saying that agents make code much cheaper, therefore there will be a large increase in demand for code. This appears to be exactly what you're describing.