I don't know enough about aircraft engine design to make a complete judgement on this. However I did find a
site that discusses that image from your first post.
The WTC was designed to withstand an
accidental hit from a plane, where it would be travelling at low speed. It wasn't designed for a plane going at top speed slamming into it. Also, the impact point on the WTC was mostly steel beams and glass, compared with the much more solid exterior of the Pentagon. Against a solid surface, only objects with sufficient mass, such as the main fuselage and the engines are going to penetrate, with the rest breaking apart on impact.
There's a little something called convergence of evidence. The eyewitness accounts for the most part agree with each other and the physical evidence, so they are likely to be mostly correct.