I completely agree with every in this article, but seems like it's just at different way of looking at the well-known software-engineering concept of "complexity." Yeah, the main difference is cognitive load is considering the complication of the system from how it effects the developer, while complexity focuses on the amount of complications in the system itself.
Yeah, if you go through this article and replace most of the places where it mentions "cognitive load" with "complexity," it still makes sense.
Yeah, this isn't a criticism of the article - In fact, there are important difference, like having more of a focus on what the dev is experiencing handling the complications of the system - But for those really interested in its concept, may want to learn about complexity too, as there is a lot of great info on this.