Not alone, I can believe, but it does seem to be an interacting factor, since LineageOS 16 can work OK....
Add this to the mix:
LG V20 h910 running LineageOS 16 -- WORKS
That said, this is an "unofficial" LineageOS build, and the phone running this configuration has severe problems. (It tends to hang within minutes of booting if a SIM card is installed.)
Also and FWIW, as noted in my first post, I had more limited -- and different -- problems with my OnePlus 5t with Tesla's 2019.8.x firmware. Specifically, calls worked fine about 1/2 the time, and the remaining 1/2 the time, the audio was garbled, but not completely absent. This obviously was not good, but it was better than the current state of it never working. If, with 2019.8.x, you had the same total failure that began for me with 2019.12.x, then that's an interesting difference.
Overall, I'd say a reasonable hypothesis at this point is that the Bluetooth stack change you propose as the cause of the problem (on the Android side) is indeed the cause of the problem, but only with certain types of phone hardware (either directly or because of different Android software configurations linked to the hardware). Furthermore, the problem clearly interacts with the Tesla software stack; and there seems to be something analogous happening on iOS devices, too.