The only way ballast would be exempt to my mind is if it did not take the machine over the allowed weight.
He may have meant to say that they had a "wavier" instead of saying they had an exemption.
I would believe a waiver from the Administrator would apply only to the one vehicle.
The only weight exemptions I know of are for parachutes or floats.
Why don't you inquire in the comments for the video..?