I think the misconception is that the fire starts in the fuel tank. Of course it doesn't. It starts somewhere else in the car, a fault in the 12v electrical system or someone dropped a cigarette end or something, and then the material of the car starts to burn. Lubricating oils, soundproofing, insulation, whatever. Soon there is a good-going inferno, which heats up the fuel tank. These are usually plastic these days, and melt. Extremely hot diesel then escapes and forms what was termed a "running fire" in the Luton report. This diesel is hot enough to burn, and sets nearby cars alight if there are any, rinse and repeat.
EV fires often start in a similar way, though it seems that their makeup makes 12v faults and so on rather less likely to cause fires. They don't have all the lubrication an ICE car has, I suppose. If an EV catches fire this way, the battery often doesn't catch fire at all. The battery in the Cybertruck that was used in a recent sabotage in America was undamaged even though the car itself was filled with fireworks and other explosive materials. Many EVs have been discovered with their batteries intact after being involved in house fires. The car has simply burned around the battery, which is undamaged. In this scenario a burning EV is less dangerous than a burning ICE car, because the fuel isn't contributing to the fire, and the "running fires" don't happen.
The big scary bogeyman scenario is where the battery itself catches fire. This seems to be uncommon. It can happen as a result of the previous scenario, occasionally, or as the result of damage in an accident, or spontaneously. Nevertheless modern batteries are quite hard to damage sufficiently to cause them to go into thermal runaway, and LFP batteries don't do it at all as far as I understand it. Another one is salt water, but again this will only cause a battery fire if the battery is damaged or faulty to begin with. (Shock-horror videos about burning Teslas after the Florida hurricane mainly consisted of multiple clips of the same blue Tesla at different stages of destruction and from different angles.) The Australian body that collects worldwide data on EV fires reports a surprisingly small number of cases of spontaneous thermal runaway going right back to 2010, and most of them seem to have been cars subject to recall for a known fault - principally the Jaguar iPace.
Stuff happens. But if you don't report on ICE fires (they're so common, they're not news) and saturate the media with horror stories about the relatively few EVs that have actually experienced battery fires, a very misleading picture emerges.
