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Is this a choice of material issue if it was the external wall insulation that caused the fire to spread?

About to order a rather large glazing unit that is 3900mm by 820mm in size. It is double glazed with no joins (so each pane of glass will be 3900 by 820). Weight is about 180kg. Asked about the warranty and the vendor said "well obviously I can't guarantee it won't spontaneously fail". I asked what he meant and he said that all glass can in theory spontaneously fail. On probing further, he tells me the inner pane will be heat treated so that if it fails it will shatter into thousands of pieces, each piece no bigger than 1cm by 1cm. I asked if heat treatment is in accordance with BS EN 14179-1 and he is going to find out. The outer pane however will just be regular glass. With heat treated glass in accordance with BS EN 14179-1the rate of failure is 1 in 400 tonnes of glass. So for a skylight this weight, there is something like a 1 in 4444 chance of failure of the inner pane (assuming both panes are of equal weight, which I think is likely as they are both are same thickness). So not too likely, though more likely than I'd like. But failure of the outer pane is much more likely and if that fails it won't shatter into tiny little pieces, it will shatter into shards. Surely that would then cause the heat soak tested inner pane to also break? This unit is going in an upstand we've built to make a skylight directly above our dining table. Not so enthusiastic about this now. Window company said laminated glass would be about £800 to £1000 more. Not sure why that's so expensive. Do people worry about this sh!t, or am I being paranoid?