They do include the entertainment system of the car, which has to have some GUI controls, probably some map rendering and speech recognition, which unsurprisingly adds up to a few more lines of code than you would expect from steering alone.

Of course, the entertainment systems of planes mostly run some kind of Linux or Windows CE, which include a lot more code than the above. AND they deploy one entertainment system for every few seats, so you would have to multiply the lines of code with that. AND all those displays have some microprocessors (or FPGAs) of their own, which add to the number of "ECUs".

In short, the article is just not fair.