The proposed solution for developers doesn't work any better; DPI is correctly calculated on desktop, but nearly always wrong on phones. So fixing sites for vertical desktop monitors will break them in most phones.
I’d express it much more strongly than you have: doing what this article suggests is catastrophically wrong. For layout purposes you must not look at physical resolution. Physical resolution should only be used so that you can render on scaled displays at higher quality, e.g. by choosing a higher-resolution image, or by scaling your canvas by devicePixelRatio so you can draw more precise lines.
The proposed solution is not just no better, but far, far worse.
