NIST flipflops on trade center explosives

The NIST, no doubt stung by sharp criticism of its probe of the collapse of the twin towers, has decided to include controlled demolition in its models of WTC7's collapse.
The agency says that of course it found no evidence of explosives but that nevertheless it will try out several scenarios of a thermite explosion at a key column.
Well, I expect that they will then use their results to "prove" that explosives weren't used.
But hasn't the NIST really discredited its investigation of the twin towers' collapse, an investigation which did not model for explosives (though it did consider the possibility of a "small bomb" but not a large one or group of bombs).

See the NIST's most recent progress report by Googling
NIST, WTC7