The last I had read, the explosion that supposedly happened on TWA 800 could not be duplicated. Jet A, kerosene, and diesel not easy to make explode. Consider the temperature and pressure in a diesel engine if you want to get in the ball park. And the fuel/air ratio has to be within a certain range for that to occur.
As for the witnesses, they are notoriously unreliable when it comes to aviation accidents. As an example, these are just some of the eyewitness reports of American Airlines Flight 587.
"The left engine was on fire."
The only eyewitness that doesn't get its facts wrong is the camera be it still or video.
I would believe the fuel tank theory if it had not happened when it did and if it had happened more than once. There are a lot of secrets out there, but one just never knows.