I'm cheerfully assuming that you're using distilled documentation and not the literal spec. If there is, say, conflicting documentation from Mozilla and Google, then we certainly have a bigger problem.
So that's the whole point. People who go on about "feature detection" and "follow the spec", and think it's that simple, really don't seem to understand what's actually going on.
[1] https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaEl...