One stream of molten unknown metal was seen. NIST said aluminium from the aircraft; I suspect lead from a battery room known to have been near the origin.
– “…therefore it’s reasonable to speculate that even more was running down the main support columns”
No, because you’re proposing demolition by melting and (1) that’s too slow to sequence, you need explosives, which weren’t heard during collapse and (2) look at the debris; the bolts were ripped out of the perimeter box-column ends; the ends weren’t melted off. You think none of the workers would have noticed had all the ends been melted off?