Eyewitnesses of ALL kinds are notoriously unreliable, something proven over and over again in all sorts of legal cases, and easily demonstrated in a variety of psychological experiments.
People want to believe otherwise, of course, because it's deeply unsettling, and people get their knowledge of the issue from TV programs and movies, where eyewitnesses are ALWAYS reliable unless they're deliberately lying.
And there have been four center fuel tank explosions on airliners..including other Boeing designs. Commercial airline accidents are rare in and of themselves and the fact it's only happened once on a 747 specifically in no way bears on whether it actually happened or not.
Making it sound like eye witnesses are never reliable and are always totally useless
is also
wholesale error, false.