Or looking at it from another angle--it happens so rarely is exactly why it gets the special attention.
Also if it did burn up all the combustibles and extinguish on it's own, then it performed as designed, especially if it was contained to only a few of the module sections.
If any section can burn out completely without catching fire to the sections next to it or immediately burning up the passenger compartment, well that is quite an accomplishment and design success by the engineers with respect to safety in the event of the bad thing happening.
Our cells have vents to open and prevent explosion, but once vented they will likely catch fire and burn. The steel floor pan would provide some shielding and won't melt like aluminum, so there would hopefully be time to get out.
kiev = kenny's innovative electric vehicle