Australopithecus - you sound like you know what you're talking about.
Could you elaborate a bit more please?
My assumption was that a catastrophic airframe break up would see fuel lines and tanks ruptured, fuel vaporised and that with hot engine cores in close proximity, some sort of flash fire albeit very brief, very similar in IR signature to a rocket exhaust plume, would happen, which is why I wondered aloud.
But then I suppose it may be possible that air frame failure at 0.8 mach might just generate a lot of large pieces, depending on the modes of failure and the breakup sequence.