Earlier quoted context omitted.
Then it sounds like you have a disagreement of terminology with FTA, since the article is using the terms like I am. Vertical scaling means increasing the serial performance of the system, and horizontal scaling means increasing the parallel performance of the system. In this sense, vertical scaling past a certain point does indeed get exponentially more expensive, while horizontal scaling almost always scales linear…
What I'm commenting on is this phrasing from the article > Vertical scaling — a bigger, exponentially more expensive server > Horizontal scaling — distribute the load over more servers
The fact that AMD chooses to package the "nodes" together on one die vs multiple doesn't change that.