The whole jet fuel can't melt steel beams theory also requires a flawed understanding of thermodynamics to work. A fire's fuel is just part of the equation needed for temperature output. A coal fire will naturally burn around 900c, but with the proper air flow behind it, you can increase it to 1200c.

The theory is also dependent on people assuming that jet fuel is the primary combustion material, instead of what it really was, the primary ignition source. It was the early 00's, a time before the age of digital storage, and that building had literally tons of paper in their storage rooms. Office fires are known to get very hot, there are plenty of pictures on the Internet of steel joists in an office building "melting" from just a regular old paper fire.

Finally, there is a difference between heat and temperature. Heat is the rate of which energy is transferred to material, temperature is how hot or cold something is. Meaning a large cooler fire may transfer more heat energy to a structure than a smaller hotter fire. It's the equivalence of throwing a bar of iron in a bonfire compared to heating one end of the iron bar with a torch.