I think the advantage is being able to move the cows on a daily basis. If I had to guess, the 20% savings comes from rotation grazing. Rotation grazing is a lot easier on your pasture, allowing you to have more cows per acre. Rotation grazing can easily be done manually -- it doesn't take much training before moving cows between paddocks is as easy as opening the gate between the two paddocks and yelling out "I've put your tasty bribe in the next paddock, come and get it". Well that's not what you yell at them, but that's what they hear.

But just because it's easy if you do it daily it quickly adds up to a lot of hours.

And the small paddocks of rotation grazing take a lot of expensive wire.