Originally Posted by Linkster

That is entirely correct - the part they left out is that the pancake process depends on the Earths gravity (kinda a real basic requirement) - and for the buildings to fall in 10 seconds as shown on video and stated in the official documentation would require that the earths gravity be changed at "ground zero" for that 10 seconds to a value many many times its real value.
Ill do the calculations later today if you really want to know how long it would take - although I would have to do it assuming no friction or delay time for each floor to slow the process down as it would take days to compute the values for each as they pancaked one upon each other. So the answer will be assuming a vacuum and even that I can see right now would be way longer than 10 seconds