[stingraycharles]

Will this not have some kind of self-reinforcing behavior, as the measurements are biased towards sites that are currently unmuted by default?

According to the MEI it actively measures user behavior and one of the most important measures is that a video is unmuted. From the document:

“The MEI is meant to allow media heavy websites (e.g. YouTube, Netflix) that rely on autoplay for their core experience. It is a non-goal to allow websites with a “good media behaviour” to autoplay without restrictions”

It doesn’t sound too good, and still doesn’t really explain how everything is seeded.