I believe you are correct
@gaswalla and this may be the reason why this feature hasn't been rolled out yet.
March 2018 builds started featuring the new MCU 2, which included not just a faster processor, but a new wiring harness for Model S and Model X, adding a new 5 GHz Wi-Fi frequency antenna and 2 external Bluetooth antennas (one in each side mirror), as opposed to MCU 1 which only has 1 internal Bluetooth antenna located within the cabin. You can see the difference of having 1 antenna on a 2017 Model S vs 2 antennas on a Performance Model 3 in
this video.