No no no, logic works the other way around: you are the one claiming that this is a new and more dangerous technology.
If you want to do that, you are the one who needs to bring evidence.
I'm simply arguing from first principles: car batteries store less energy than fuel tanks and release that energy slower and over a longer period of time in a fire. Ergo, they are safer for pretty obvious reasons.
Most car fires do not actually involve the entire gasoline tank catching alight; as the gas tank is well-protected and not particularly near sources of ignition. An engine bay fire is much more common.
If gasoline is spilled, foam works well to extinguish it and keep it from igniting.
Once a gasoline fire is out and cool, it is going to stay that way,
Lithium-ion battery fires are self-sustaining thermal runaways. You cannot put out such a battery fire by smothering it; it does not need oxygen from the air. All you can do is try to keep it cool by running water on it.
Even after such a fire seems cool, it can reignite unexpectedly.
The actual gross volume of energy is not necessarily what makes fighting a fire dangerous or not; it's the unpredictability. Firefighters may be more worried about compressed gas-strut explosions (from hatches, hoods etc) than they are about the gas tank exploding.
I'm simply arguing from first principles: car batteries store less energy than fuel tanks and release that energy slower and over a longer period of time in a fire. Ergo, they are safer for pretty obvious reasons.