Bernard W. Joseph, mathematician: "How could they stand in the center of the circle? If it's a fly-cutter, you would have to keep jumping over the revolving arm. If it's a core cutter, you can't fit inside the tube. This is hard to believe.
Russell Styles: They could have been cutting a noncircular hole in a slab with a diamond saw. Such a hole could be easily large enough for two people.
Bernard: "Any floor of that sort would use reinforcing rods. They would have had to not only chop out the concrete, but also cut the rebar. I still think that it's mechanically improbable.