You are incorrect. I stream music on my S3 via BT in my car all the time. Unfortunately, my car does not understand the USB protocols the S3 uses. I have the Verizon version.
No problem streaming music to my 2012 Stock Honda Civic, wife's Alpine stereo and my Moto S10 headset.
Are you talking about using Cyberon Voice Commander? Or the S-Voice?
thanks, Linda
If you have issues streaming audio, I would highly recommend to unpair the phone from the car, then try to pair it up again. This time, wait for the phone to ask if you want to give permission for it to stream the music. The request will only last a few seconds, so don't look away long. Many people having this problem did not accept this request in time the first time they paired the phone. BTW, this is an Android thing, not specific to the SIII. And as they say, YMMV.