What I'm curious about is what the FDNY thought was going to happen after they "abandoned" the building. Especially since the building was warping. Presumably there was some discussion: Did the conversation go like this:
"If we don't put out these fires, the whole building is going to come down!"
"There's no way we're going to get it out, so it's going to come down."
"What about the buildings / people around it?"
"Oh, don't worry, it'll come more or less straight down."
That doesn't seem likely. They can't have known how catastrophic their decision not to fight the fire was. It's hard to imagine them knowingly letting a 47 story building totally collapse in the middle of a city, even under the exceptional circumstances of 9/11.
As always, I could be wrong and they were exactly that conscious about it all. Whatever their thinking, it would be great stuff for the book, and it would also clarify the physics. After all, it's their engineering intuitions that would have guided their expectations about how the building would behave with uncontrolled fires in the hours after they pulled out the crews.