I laughed, but is that really true? You're going to have a lot of batteries/cells in one place, and one will inevitably start barbecue. Isn't the question whether the rest joins?
I suppose it is probably hard to engineer a battery that is prone to spontaneous barbecues but resistant to the influence of outside barbecues. But I'm not sure I agree that it's just a numbers game that if you put enough of something in one spot, some of them are bound to suddenly catch fire without outside intervention.