I can see how the phones hardware/software can make a difference but I still say the Subaru mic is the real issue here. Also, I did make a note on how the placement of the phone does have an effect on the call quality, so interference is always gonna play a factor, whether big or small, on the call quality. However, placement of the phones and lowering the gain level to 1 helps, and of course packing the dead/open space between the map light and roof helps as well, but it's not the right solution to this. Ultimately, this problem should fall back on the manufacturer itself.
Can anyone make this happen?