Sorry for resurrecting an old thread but I have this exact problem and I can't believe it hasn't yet been fixed. The bluetooth headset profile should never be used to pass through multimedia audio only calls.

It seems that this can be fixed through changing pulse audio routing policies. If someone who is knowledgable about pulse audio could at least point me to some documentation on changing audio routing policies I would be grateful.

Also this has been discussed here and filed as a bug here though for some reason it has been marked invalid even though every other phone I've owned has obeyed the spec and only routed call audio to a Headset Profile device and not system wide audio.