I don't think the graph agrees with the essay.

In the essay, the "unintentional moderate" is defined as someone who holds all kinds of views, some from the far left, some from the far right, some from the middle - but by chance the average of their views makes them a moderate.

I had to go looking for that, because the graph doesn't show that at all. I think the graph is a bad take on the ideas in Paul Graham's article.