I have the same issue with my BT earpiece. I read on another thread that this is normal which I can't believe should be the case.

Maybe there is a config file for the device which you could edit to take away the a2dp ability from the headset? It is annoying as I listen to podcasts on my way to work through the 3.5mm jack into my head unit but can't even have the BT earpiece turned on as it takes over all the audio.