Yes, it is considered.
Potential energy of one of the twin towers in earth's gravitation field relative to ground level can be estimated as follows:
E = m*g*h (m=mass of building, g=gravitational acceleration=9.81m/s
2, h=averge height of mass before fall)
From
http://www.journalof911studies.com/volume/200703/GUrich/MassAndPeWtc.pdf I get
m= 288,100,000 kg
Total height of a tower is 415m. The center of mass would not be at half that height but lower. One can assume 30% of total height (I can give reason if so desired):
h=125m
So total gravitational energy is on the order of 3.53*10
11 J
1 ton of TNT has an energy equivalent of 4.184 × 10
9 J
So the potential energy of the mass of one tower was equivalent to about 85 tons of TNT. Nuclear weapons start at 300 tons TNT.
A modern nuclear power plant has typically a power output on the order of 1*10
9J/s.
To dustify one tower in 14 s, the power needed is 3.53*10
11 J / 14s = 25*10
9J/s
That is the power output of 25 modern large nuclear power plants.