It's interesting to see how a big company with a lot of talented engineers would build a brand-new web app, since there's so many ways to achieve similar results.

CSS is a big part of the web and lots of people use it every day. I find this post interesting because it inspects a world-class app used by millions of people, and it showcases some of CSS’s latest capabilities, plus it has nice graphics illustrating the findings!

It's very good educational content for people who don't really know all the intricacies of modern CSS (e.g. myself).

Copying something Meta did and playing with it just feels more interesting than an abstract example out of thin air.