It seems that in that rig, without an enclosure, they are limited to shooting in the dark using light painting lest they capture the background. In this "shadowless" rig with the overhead lighting and white background they have more options. He even mentions the possibility of painting the inside which makes me think they might be thinking of doing a green screen. They do have to worry about the camera holes which means they'll probably have to shoot with an upward angle.
EDIT: Found some of a similar rig they built in the comments of the same page: http://www.petapixel.com/2012/12/17/project-uses-a-bullet-ti...