Mac
I did read the article;
I quote "The floor construction is of prefabricated trussed steel, only 33 inches in depth, that spans the full 60 feet to the core, and also acts as a diaphragm to stiffen the outside wall against lateral buckling forces from wind-load pressures."
The floor is subject to compression on the top and tension on the bottom of the truss. When subjected to heat the steel lost its strength, especially in tension and collapsed onto the floor below, coming away from the side walls. Add to that the weight of the floors above the fire and the floors were severely overloaded.
I am not an engineer however I would have thought that the lightweight trussed beams were considerably weaker when heated than a equivalent, comparable RSJ.
When you see the north tower collapse it is plain that the floors gave way before the outside walls.
Read the article again Mac, I agree entirely with the consensus view of those writing it.