I've had a hunch it's about the shrinking width of pages. The text-width is about 11-13 words (at a max-width of 728) and the author seems to have written around this.
Because it's so thin, anything longer than 12 words becomes a paragraph which "slows" the reader, so there are a lot of punchy short sentences. This style would look silly if it was written on a wider left-aligned blog.
That's funny you mention text-width, I've noticed that with "punchy" articles like these.
Alternatively, when I see the old-school blogs that fill the entire page-width, I get the instant feeling I'm about to read something opinionated and quixotic.
Sure enough, the last HN article with that style hit it-- let's rescue the web by sending around WASM-blobs to be rendered to a common Wayland-like compositing surface. Thanks again, default CSS!
Because it's so thin, anything longer than 12 words becomes a paragraph which "slows" the reader, so there are a lot of punchy short sentences. This style would look silly if it was written on a wider left-aligned blog.