Perhaps it imposes some restrictions, like using TPMs, but I don't think it excludes what the author is suggesting, which is the ability to run as root.
Case in point: every popular desktop PC let's you run as root, and also watch DRM content. They aren't totally mutually exclusive.
You can't play 4K Netflix on Linux, period. Because of DRM. Before you say "this is just a Netflix issue" - you can't play 4K Prime Video on Linux either. Nor 4K Disney+. And many other services. Piracy is the only way to watch most 4K streaming content on Linux. You may have the most capable and up-to-date hardware on the market, you still can't.
Yeah, that realization is what killed my attempt at replacing my Nvidia Shield TV with my home-built SteamOS box. I got everything "working" in the most technical sense, but I was limited to 720p on Hulu, and that ended up driving us crazy. I know that the box is capable of streaming 4K video just fine, because I was able to stream my 4K Blu-ray rips from my Jellyfin server just fine, so this limitation is purely artificial.
I did do some experimentation with VMs and emulation and whatnot, but I never got anything that worked consistently enough to use full-time, so I bit the bullet and plugged my Nvidia Shield TV back in.
Case in point: every popular desktop PC let's you run as root, and also watch DRM content. They aren't totally mutually exclusive.