No, it's also an attack on the actual wireless key which is used to open and start the car. It's just making the car "think" that the key is inside, so you just press the Start button and the car starts, after which you drive it away like normal.
Fair, but only on cars which have only passive security (that is - where you don't need to use the fob to unlock the car and you don't need to use a physical key to turn the ignition).
Which is of course the stock configuration on most modern luxury vehicles.
Most new cars which have keyless systems work exactly like that, nothing to do with luxury cars.