ok, your original post was somewhat misleading then because of lack of clarity on how/what you were doing
i'm still not completely sold on the non phone related voice input/commands going thru the car system (reading texts to you yes, i'll believe that, if you're connected/selected to the audio-bluetooth-for playing music from phone, it shouldn't do anything other than do calls if you are in radio/cd/usb)
i dont suppose you could video you using these other things? i'd very much like to see this in action
you may have to physically put the phone outside the car to make sure it isn't the phone picking up the voice 'over the air' as it were.
its not so much a matter of what the phone os is capable of supporting(they call can handle myriad voice commands) but what the mazda system does (i used to have a winmo phone and i liked the reading texts over bluetooth ability, android doesn't normally support that natively

but thats neither here nor there, i can dictate texts to the phone though using built in functions)
unlike a BT headset, when you use the call button its doing the work in the head unit and just porting the audio thru the bluetooth connection with the phone (which is why when you adjust the volume on the headunit it doesn't change the volume on the phone), where with a bluetooth headset its just acting as a conduit to the phone sending everything for the phone to discern what to do with, ie adjusting volume on a headset actually changes the handsets volume levels (as seen on the screen)
otherwise the mazda doesn't support any sort of interaction thru the phone other than their established commands (notcool)
i do agree that the mazda voice control isn't as good as whats built into most phones but its better than the tomtom systems voice control