Possibly, I suppose. Nothing is stopping them from doing that. Though it would be a huge dick move, and it might end up exposing them to a lot more warranty claims than they planned on if something goes wrong with that 'car kills itself if it goes too long without cell signal' system.

Like ... suppose a perfectly normal owner leaves his car parked inside an underground parking garage or a metal shed while he goes on vacation ... and then comes back a few weeks to a month later and finds out that his car won't work at all? Now the dealership is on the hook for towing fees, half an hour of technician labor to reset the system, and maybe even the use of a loaner car for a day. That potential cost seems to really outweigh the 'benefit' of preventing any owner from purposefully disconnecting their car.

Anyway, if you somehow end up with a car like that, then you might need to be a bit more creative in the solution: instead of connecting the antenna wire directly to a resistor, you'll need to connect it with a 2-way switch. One position on the switch connects it to a grounded resistor, the other position connects it to the original antenna. Then you just have to remember to occasionally turn the car's spyware on for a few minutes every month or two, just long enough to reset its internal self-destruct timer. (Though it is possible that it might be collecting data while disconnected and then sending that collected data once the connection is reestablished. In that case, this isn't a very good solution, though it would at least prevent them from fucking with you in real time.)