The fact is these are high tech machines. To follow your example with the car, you don't need to replace the battery but an ECU, for which there are no available design and you have no idea how to build it.
Add to this that probably if you make a mistake in your try, you destroy the machine.

Basically what ASLM is saying is that they can brick the machine with a software update and even if not bricked the machine cannot run long without specialized maintenance and spare parts (that they obviously will not provide anymore). True, China can try to clone them, but even if/when understand how to make them, you then need to make them, a thing which seems out of question for now for China (else they already would have such machines).