Seeing as that design is never mentioned in respects to ergonomics and certainly wouldn't "bounce" anything, I strongly suspect the quoted passage was referring to the inflated balls you sit on.
http://images.businessweek.com/mz/10/19/0509_chairs.pdf
I'm just going to continue as usual, using the ball chair and alternating with a normal chair if needed. My spine feels great and definitely has a more natural shape when sitting on the ball vs. a normal chair.