It doesn't really change anything for this workout. This chain never actually lays on the ground, so no weight is really removed. Basically he has the weight on him through the whole movement and it never changes.
They're often used on movements like bench press or deadlifts to add weight as you get further along the movement. The chain will be longer and start out mostly on the ground so it's not adding that much weight, then when get the bar further up, more chain comes with it, so it gets heavier.
All that to say, he's still a freak and it's insane that he makes this look as easy as it is.