Nonsense.
This "outer shell" theory is just the latest in a parade of discredited and embarrassing theories from our brilliant engineers at NIST.
Remember the "Pancake" theory? How about the "Thermal Expansion" theory? All quietly retired in a wave of ridicule.
Now they claim that a 47 story steel structure was designed with an outer shell, and a interior structure that could collapse inside the shell, out of view of the world, and then the outer shell collapsed straight down afterwards.
But the reality is the structure was a complete, interdependent unit, with steel cross-bracing and load sharing, unitized to withstand high velocity wind and twisting.
Just visualize the entire "inside" failing due to one column at the far East side, and precipitating in a complete collapse of the whole internal structure, while this "shell" of the outside walls just sat there in plain sight until it too fell straight down as a complete unit of the east, north, west and south walls and the entire roof.
