Should we be all that surprised?
Just the other day we showed you all a brief (and still growing) list of cars that have fake engine sounds. Automakers have come up with different names for their own versions of a system that essentially does the same thing. For example: Ford's is Active Noise Control. BMW has Active Sound Design. Same idea. Different bullshit names. And in BMW's case the system is hackable. It's already been done and proven. Someone has taken the "sound" of an M4 and given it to their M135i.
It's pretty much just a matter of swapping out the file. See for yourself in the sound demonstration ahead. The owner here proves that for those who know how, it's a fairly simple hack job.