https://w3c.github.io/mediacapture-main/ does not mention it, and it appears to be redundant with the muted boolean attribute.

It's possible to measure usage when readyState is accessed and "muted" is returned, but that's not necessarily a good estimate of the risk, as the calling code *could* be something like this:

if (track.readyState != "live" || track.muted || !track.enabled) {
  /* do stuff */
}

Returning "live" instead of "muted" for this could would not change anything.

Using httparchive looks tricky because the strings "readyState" and "muted" often appear close together where they are related to media elements, but with a detailed analysis it would be possible to look for cases that are really from MediaStreamTrack.