There is another thing going on, at least for iPhone users, in that it won't let the car automatically connect. You must go to the hotspot screen on your phone first to allow "others to connect". The Tesla is an "Other". Your Apple devices can connect automatically but not the others. This is a security feature of the phone.
What always happens to me is that the car automatically goes to LTE because it can't see the hotspot until I do that, and then I have to turn wifi on manually. Once turned on it finds the hotspot and connects, and remembers the "Remain connected in drive" setting. Only if I remember to turn the phone hotspot on first, before I put it in drive, will it connect automatically, and then only sometimes depending on how long I wait.
Another thing is that I tried to use programmed automation on the phone to automatically bring the hotspot up when it connected to the car's bluetooth and it turned out to be more trouble than it was worth. You still had to force the applet to run. It was easier to just bring up the screen manually.