Actually not BS, see the Broad Group's web site and their timelapse of the 'demo' project [1]. They don't count the time to put in the foundation and drive the pilings, just the erection part. That part consists entirely of lifting pre-fabricated sections in place, connecting pipes and wires, welding to the rest of the building and moving on to the next one.

[1] http://www.youtube.com/watch?v=Hdpf-MQM9vY&noredirect=1

I've seen that already, and yes, it's impressive, but watch and see, this isn't going to be built in 90 days, or next year. Probably never.