You are both ignoring these facts:
The majority of the core was elevator shafts and air ducts.
There is very little to burn in hallways and washrooms.
The available fuel [office contents] was spread out resulting in less fuel per sq. ft. of floor space.
Given the limited amount of fuel in the core area, the limited areas where there was any fuel at all, and the fact that fires in the core area would be oxygen starved, there is no justification for speculating that the core columns exceeded 250°C
[qimg]http://img5.imageshack.us/img5/1596/coreareafloorplan.jpg[/qimg]