I'm guessing you could get rear-ended a bunch of times without fuel spilling. I bet fuel only spilled during one specific test crash but, since the spilled amount was more than the new standards allow, Mazda felt they needed to be pro-active. And, even if some fuel did spill in a hard accident, it doesn't necessarily spill on an ignition source and ignite. And if it did ignite, an uninjured driver in reasonable physical condition could probably clear the car quickly enough to escape burns. It would take the perfect confluence of events for this to be a problem. If it did happen, it would almost certainly be a very hard freeway rear end event with the ignition source coming from another vehicle (because the CX-5 exhaust is not hot enough to act as an ignition source unless the fuel made it's way to the catalytic converter area.
Not saying it couldn't happen or at some point in the CX-5 fleets lifespan, not saying it won't happen or that it shouldn't be repaired in a timely fashion. I AM saying, it shouldn't be alarming (in the same sense that you shouldn't worry about an airliners fuel tank exploding when you board a plane (although it COULD).