"In this video I discuss how YouTube is artificially slowing down videos in the Firefox browser artificially to probably get people to use Chromium browsers that Google has more control over."
The video is bunk, the original "analysis" was wrong, they didn't look up what the function actually does, the function is showing up in other browsers. It's pretty clear this is an A/B test rolling out that's fetching something behind the scenes that's broken for a bunch of people.
Jumped to a conclusion without even understanding the subject at hand.