I feel like the article / author is perhaps attacked for missing key front end concepts such as square/circle (if I got that right, it's been years since I touched front end), but the premise still stands - which is exactly what you and gp says: A simple UI element shouldn't waste resources like this.
I was thinking that even a higher resolution scaled down animated gif would be better, wasting memory is perhaps better than cpu, but ultimately a bug report/ optimisation request for the Chromium browser would be a big win.
Hardware keeps evolving, yet inefficient software always seems to find ways to catch up to this.