> the author mentions JavaScript preventing rendering which isn't the case for anybody who is looking to optimize their site for speed
Rewriting your JS to be async-ready can be a huge lift. Not every site pursuing frontend performance is ready to do that, much less has done it. I think this article certainly has an audience.
> I have not run into layout janks when I have used critical path CSS
Call me a skeptic :) if a user is able to scroll beyond the fold before the CSS loads, you've introduced CLS. Spoiler: they will always be able to.
Critical CSS and 0 CLS happens only when you create skeleton placeholder components for everything below the fold as well. There are no "tool/settings" that will do this automatically.