I’m guessing neither of you is actually interested in getting a Tesla, but I wouldn’t worry about this particular issue.
Your phone can communicate with multiple Bluetooth devices without trouble, so unlocking your car will have no bearing on your HA connection. And Tesla provides an unlock keycard to authenticate your phone or unlock the car without the phone present.
Bluetooth has no problem with multiple simultaneous data-only connections; it’s the audio/handsfree connections where you have to choose, since generally you don’t want more than one of those active.
So the only Bluetooth issue I have with our Tesla also applies to our other non-Tesla cars: my phone automatically switches audio to the car when I’m in it, but doesn’t automatically switch back to the HAs when I leave the car.