Consider a damaged NM cable that develops a parallel or series arc. The bare equipment ground in between the conductors involved should receive sufficient leakage current to clear the arc long before the arc is at the threshold needed for the arc-fault detection circuit.
30 mA RCD (GFI) testers are standard here, since 30 mA RCD:s are the norm. I'm on the other side of the pond... Perhaps Europeans are less sensitive to electricity