You raise an interesting point there, DV. Pressure testing a system to 50 psi that is known to surge to 80 psi would appear to be an oversight. Way above my pay grade, maybe Tucumseh will help you out there.
Your statement leads me to draw two conclusions (from a distance)
That the people at Kinloss are looking at either an AAR pipe failure, or No1 tank failing to shut off during AAR and developing a major leak.
You still need an ignition source. To those of us in the business, fuel leaks are common, and aviation fuel doesn't burn that easily. I can't imagine that the BoI will identify an ignition source.
I expect the BoI will be 30 pages long, but the only certainty is that -
'After AAR, a catastrophic fire in the bomb bay resulted in the loss of the aircraft'
I'm retiring from this thread to wait for the BoI
SPHLC