I just figured out the catch… to hold irregular objects (that chair seat for example) the dogs need to move independently, and they don't. But you could hold symmetrical objects or produce custome jaws for odd shape, only worth doing if you are making a lot though.
To my eye they do appear to be independenly movable, firstly by having them set to the aprox position before engaging with the central gear, and secondly it seems to show the jaw nuts are some sort of half nut arrangement.
Seems a lot of trouble just for an April 1st joke.
Just looked at all the different tools. If you read the 'second pages' you'll discover they all really work, although they are impractical (except the story tape which is real).