One can argue either way on whether the fire started in an EV, or somewhere else, maybe even an ICE.
You are not wrong in saying the older and still predominant batteries are the main risk in terms of a self-sustaining reaction.
The point is once an EV got involved, of any battery type, one is looking at an uncontrolled release of up to 60 KWh of stored energy.
The First Law of Thermodynamics says all forms of energy are inter-convertible. Properly directed, the electrical energy in an EV becomes enough converted kinetic energy to take said EV 400 - 500 km. If the electrical energy becomes heat instead, thermal runaway up to 900 C, or more. Anything organic in that environment becomes part of the conflagration.
It would be an interesting experiment, if somewhat expensive, to park three ICE's together, then measure the rate of spread and intensity from the middle vehicle after initiating combustion there. I suspect both variables would not be as extreme as with three EV's parked together.