" and there were no plans for helicopter rescues from the roof, as the NYPD deemed it too unsafe to attempt due to dense clouds of smoke and rooftop antennas."

If you're referring the 9/11 situation, this is the reason why it wasn't attempted - from https://en.wikipedia.org/wiki/Brian_Clark_(September_11_surv...

That said, I suspect that had they known the towers were going to go down within 2 hours, there might have been some different decisions made. But that's just hindsight. :/

I'm guessing the tremendous amount of smoke and all the obstructions on the roof would have made this impractical. The situation wouldn't have been aided by helicopters falling on to rescuers below.