Dave,
To my mind there was a source of ignition present for a long time, it didn't cause a fire because fuel wasn't also present.
Whilst that is true, the emphasis must be on the big NO NO being an ignition source. This was totally unacceptable in the aircraft design. Fuel as a liquid has a habit of getting in places it shouldn't, so you must take that into account in aircraft design and make attempts to ensure it can do no harm if it does. This is why you have to blame the ignition source, not the fuel. To put it in probability terms, you cannot preclude a leak from happening during the life of an aircraft by any stretch of the imagination - hence this shows that ignition sources must be absolutely totally avoided where fuel can come into contact with one otherwise you could never prove it met the required 10-7 hull loss rate (which is basically similar to saying never happens during an aircraft life) and hence could never be certified.
I'm not saying leaks are not a bad thing, just that you can't totally eliminate them, hence you MUST address the other risks.