so the industry has had ONLY ONE event of a lithium-battery fire, from a device while in-use???
You appear to be downplaying a hazard, tantamount to dismissing it out of hand.
You might have missed the destruction of UPS 6 recently, likely the result of a fire initiated by lithium batteries. While your question asks about a "device while in use," do we really care if it's a computer in use, one in storage, a flashlight, or a box of batteries on the main cargo deck? Burned to death is rather final, and the hazard should never be understated.