It's the second to last paragraph, when someone reading the essay may have already formed a hard to dislodge opinion on the kind of writing PG means. And indeed, many people here on HN did so.

The order of paragraphs, how early in the text ideas or clarifications are introduced, etc, all make for clear writing.

I'd say this is an example of an essay that lacks clarity, i.e. one that is not "good writing".