Yeah, I was a little troubled by this assertion, and by the figure of half a million people. I hope the Jerusalem Post didn't have their chain yanked by some con man posing as a retired architect. I posted the story because of the assertion that the floors were designed to self-seal. If this is true, then it is possible that tens of thousands of people were sealed in one great big coffin, with no hope of emerging.
I saw an interview with a survivor who said that the fire doors were locked (which would be consistent with the self-sealing assertion), and that they had to break the window of a Barnes and Noble bookshop in the lobby, go through the bookshop, down an escalator, through the basement, and back up another escalator before they could find an exit to the street.