I don't see any evidence that this exploit is related to the GUI at all. The GUI just happens to be the easiest way to do it. Other commenters have mentioned that you can use the exploit with `su`.

In any case, in a desktop system you shove everything together and then try to modularize it with good design and weak tools like UNIX processes. In a car, the safety-critical systems are literally running on separate hardware with limited communication over a specialized data bus. Of course it's still possible for them to have bugs or even exploits, but the complexity of the infotainment system is irrelevant, aside from making it a potential jumping-off point for using an exploit in the safety-critical systems.

Counting the infotainment system here makes about as much sense as counting the number of lines in Windows when talking about a Mac vulnerability because a Windows machine could be used to launch an attack.