um... no... YOU dont get it. The WHOLE building falls down basically level and symmetrical. ALL the support columns would have to be severed at the same time (from an office fire) and because of the admitted free fall the floors BELOW would have to be completely out of the way for any free fall to occur. therefore the bottom floors would have to have collapsed and started their fall before the upper floors.You just don't get it do you, there are subtle changes of acceleration in the external walls all the way down the ground.
The cores are collapsing ahead of the walls, pulling them in, and as they go through floors ahead of the walls being pulled in theres a series of jolts over G all the way down as the spandrels initially tug against the resistance of the outer structure, when that resistance is overcome, there is a split second over G, the NIST did not figure that into their models, and after being told about their error, added foot-notes stating this on release, whereas they averaged the speed of collapse only from when the roof-line started to descend, and they did it in sections, their averages for one section was free-fall, whereas in reality it was an average of over G and under G accelerations far to subtle for the naked eye to see.