You are really discounting the ingenuity of criminals. If they can steal 4 tires with wheel locks off your car, they can steal your undercarriage battery.
EV batteries are becoming STRUCTURAL, meaning they make up the core vehicle shell of the car, use hardened steel reinforcement and weight 1-2K pounds. They're also super dangerous if punctured. It would be easier to steal the whole vehicle than to steal the battery alone.
I'd go so far as to say that an EV is a glorified "battery with wheels" since the actual drive components are a minority of the weight/complexity/cost. If a criminal can steal the whole EV, they will, if they cannot then stealing the battery alone isn't realistic.
As connected as modern EV cars are, stealing one would seem like a dumb decision since they'll know exactly where the car is. I know chop shops are quick, but I still wouldn't want to knowingly bring something with tracking devices into my criminal lair.
Really? I'm pretty sure I have the tools in my garage to steal 4 wheels with locking nuts. I'm absolutely certain I couldn't steal the battery in my EV without stealing the whole EV. Which has a GPS tracker built into it.