Not sure what that's got to do with anything. The fires are caused by the extremely flammable organic solvents used in lithium batteries.
I suspect that's what sustains the fire. Quite often what causes the fire is either short circuits caused by contamination of the battery with metal particles, which may puncture the extremely thin separator layers, or the fact that mistreated batteries can begin to form metallic lithium on the electrodes, the same way an electroplating bath operates. Ordinarily, lithium ion batteries contain absolutely no metallic lithium (other lithium-based batteries do). They contain lithium salts, compounds of lithium. If actual metallic lithium forms, a fire risk is created, since lithium is pyrophoric - that is, it will spontaneously catch fire in air, at normal temperatures.
Again, there is not actually supposed to be any metallic lithium in lithium-ion batteries. If there is, the battery is broken.
If it was just the lithium it wouldn't be so bad, but as you say, other battery components tend to be ignited by the flammable metal or the heat of a short, and that's where the real issue comes from. Eight grams of lithium is actually quite a lot by volume, as lithium isn't very dense, but the real problem is burning solvents and plastics.