I think mini-nukes had to be used to completely flatten/pulverize/disintegrate those massive structures... I am primarily unsure about how much steel was actually vaporized. Lots of outer wall sections and core columns just seem to have disappeared... but it's not clear to me how these could have been obliterated without the use of huge blinding bombs. And how did so much of the internal objects including floor slabs, get completely disintegrated?
The only thing, as I pointed out in my last post, is that it's just bloody hard to know how much of the structure was indeed obliterated, given the public information we have. However, the picture we have show there WAS a HUGE AMOUNT of STEEL DEBRIS, contra to Judy Wood/Morgan Reynolds. Joel Meyerowitz's book "Aftermath" shows this very well, but so do many other pics of ground zero from other sources. The big question is what was in the footprint of the towers-- and how far down the debris went. That makes all the difference.