You're right. The fire that has torched quite a few Tesla's, is a chemical fire, started by a battery internal short-circuit (a few houses have been burnt out by e-bike battery packs doing the same trick).
As the fire is fed with all that it needs, then trying to extinguish it by starving it of oxygen/air / smothering it.... doesn't work.
In addition, the smoke/fumes emitted are VERY nasty. It wasn't widely broadcast, but when they introduced the "TT Zero" bike race at the IoM - the Marshals were specially trained, issued with BA, & warned to approach and E-bike fire from down-wind.
Also, in the build-up to introducing the electric race bike series into MotoGP.... the entire grids-worth of bikes went up in a massive conflagration at Jerez circuit. The circuits Pit Lane & garages, Stadiums etc weren't destroyed - because the e-bikes had been parked up instead in a marquee/tented area in the infield well away from the circuit infrastructure. A wise move.... but begs the question of why that wise move was seen as so necessary, eh?
Apparently, the energy density crammed into a modern EV battery - is higher than TNT - which in effect says that an EV.... is a wheeled bomb.
Granted, the likelihood of an EV battery pack shorting, igniting and then burning for hours is low... but the "seriousness of consequences" if it happens, is not good at all.
