I still notice the low bit-rate audio quality even after sending the unit back and them reporting that they did not find anything wrong with it, and them returning it. Even when I use wired carplay. This leads me to believe the audio processor is just set to low bitrate, similarly to how some bluetooth devices stream higher bitrate audio for media, but reduces to a lower muffled bitrate for calls to minimize latency. Is is possible that the audio is somehow stuck on the handsfree audio bitrate?
I recommend you to get back to our technical team (if not done already), they will help.