It's the other way around: they phone home so that they can be bricked, or at the very least have important features disabled at Tesla's whim.
What you're suggesting can't work because there isn't cell reception everywhere, but of course that hasn't stopped car rental companies (I think) implementing exactly that with the predictable result of people being stranded in remote locations.
The real danger is that someone from Tesla is here reading your comment and putting it on the to do list.
What I'm really asking is if you are allowed to block the phone home process. Or, in superlative language that I suspect would resonate more with Tesla fans, "in the event of an apocalypse does your Tesla automatically brick itself or does it continue to function?"
There's lots of research here in the Tesla hacker community. The car continues to function. The easiest (not trivial, but easiest) way to test it yourself is to remove the SIM and disable wifi -- the non-network features of the car continue to work indefinitely. There are even some third parties who support early Tesla vehicles, on stock firmwares, in part by fully blocking comms with Tesla.
What you're suggesting can't work because there isn't cell reception everywhere, but of course that hasn't stopped car rental companies (I think) implementing exactly that with the predictable result of people being stranded in remote locations.
The real danger is that someone from Tesla is here reading your comment and putting it on the to do list.