The difference is that the batteries can ignite without an external heat source.
That doesn't necessarily make them more dangerous. I have a friend who lost a home to a fire that started in the engine compartment of a car in the garage. It was probably a leaky fuel line dripping onto a hot engine component. In your reconing is that an internal or an external heat source? Of order half a dozen car fires happen during a typical commute day on SF bay area freeways, and that's not counting the fires that start because of collisions.
It doesn't seem that likely that Teslas are any more fire prone than any other car. The rates for gasoline cars have about one serious (i.e. reported to police) fire per 18 million miles. If the average car goes 180K miles, that's about 1% that go up in flames at some point. The average Tesla hasn't gone that far, and I don't know what the fleet mileage is, but I'll be surprised if they are that flammable.
Doubt isn't the opposite of faith; it is an element of faith. - Paul Tillich, German theologian and historian