> I removed a non-trivial amount of CSS (now about ~5KB of CSS over the wire for the entire site)
That's around 2% of the size of the single page of that article, it absolutely is a trivial amount, especially when it complexifies so much the maintenance or addition of the website.
In fairness, the page loads two enormous fonts. Lots of blogs just use system fonts, so the advice is generally useful if you're trying to reduce your own site size. The total payload without the fonts are around 12kb, so reducing the CSS to 5kb is a fairly big deal. Without the fonts, the entire site could be delivered in the first TCP packet.
That's around 2% of the size of the single page of that article, it absolutely is a trivial amount, especially when it complexifies so much the maintenance or addition of the website.