No doubt a fire as intense as you describe would damage or cause buckling but the question is with these accidents did it cause a total symmetrical failure?
The failure in the WTC towers was not in load bearing structural steal. The Towers were internally stressed by the equivalent of guy wires, very light steel members reinforcing the concrete floors. When these lightweight members sagged there was nothing to keep the load bearing members stable.
But more specifically, there was no heavy steel supporting the floors. When the lightweight steel failed, tons of concrete pancaked onto the lower floors.