I installed Chrome 70 beta and tried the playlist. Sure enough, when I right-clicked and chose "Stats for nerds", it said the video was in AV1 format. I tried the URL in 4K Video Downloader and it showed a bunch of unknown entries in the MP4 category.
The article mentioned AV1 only being available up to 480p, so I wondered why there were so many options and why they went up to 40.3 MiB. I downloaded the largest one and tried to play it. MPC-HC didn't recognize the codec but thankfully I just had to update it. Once I did, I was able to play the video.
The file turned out to be 1080p, so YouTube must have encoded higher resolutions after the article was written. MPC-HC was able to play it at the full 29.97 fps on an Intel Core 2 Quad CPU.
It also played surprisingly well in the browser at 1080p.
The only issue I noticed is that the downloaded file had no sound.