They are not metallurgist, which once again brings us back to my original comment about firefighters. With the large amount of aluminum that was used in the facade of the WTC buildings and in the construction of the B-767s that struck them, and add to the fact that temperatures were high enough to melt aluminum but not steel, it should be of no real mystery that any molten metal they saw was nor steel. In other words, there was nothing there to produce molten steel at ground zero.
All you have to do is to produced evidence of a catalytic reaction that can produce molten steel other than from torches from clean-up crews, short of that, you have no case.
Which brings us back to the argument that firefighters and others who are not experts in identifying molten metal nor are they metallurgist.