I think part of it is NIST has worded it in such a way that the layperson, without the assumptions that professionals would make, would find misleading, or at minimum confusing.
In a nutshell, after reading this section of the report, I get the following cole's notes version...
1. Heat on numerous floors, led to expansion of the steel in many locations, especially on floors 8-14.
2. This expansion (and contraction) lead to a combination of weakening and sheering forces, that caused BREAKAGE of the connections etc...
3. These breakages led to the internal collapsing of numerous floors, but in particular a stretch of floors from the 13th down until the 5th floor.
4. The loss of these floors left column 79 unsupported for a span of 8-9 floors, which led to the buckling of column 79, which was the initiating event of the total collapse.
Anyone arguing the above, and if so, please clarify where I have got it wrong.
TAM
