Thanks, that is indeed so. I must say that the Chrome team have been really fantastic about it (they reached out to me after asking on twitter).
It's just the age old resources problem: not only do you have to change the frontend, you also need to make changes on the server. That more than doubles the work (quadruples in our case because the server requires far more QA effort).
That comes at the cost of other features, features which are more valuable.
You can use the Web Audio API (getusermedia) and set an audio pipeline filter that stops sending data while a boolean flag is set.
I don't know if you mean a different API entirely, and I don't mean to disagree---just FYI :)