Yeah, I'm kind of legit irritated at this. I tagged xbox/harmonix/fusergame on twitter and posted a screen of the "Astronauts on the Couch" when you can't stream to twitch asking what was going on.
It's pretty obvious what's going on. It's copyrighted music, and it can't be streamed/recorded. It'd lead to suspensions or bans, so it's disabled all together.