Do you have examples of cars (that aren't Teslas, perhaps, since they don't play by normal car rules) having been disabled due to lack of cell service?
Many cars have something similar (remove SIM card, cut antenna) that allows them to keep working without connectivity
Incidentally, this link recommends termination resistors, which I think are the better answer if there's a suitable connector (which I imagine is the case for most cars). If it's not terminated, I believe it can still pick up a nontrivial signal.