On thing I like to add, If you are doing root pruning in the spring or summer, your fig tree will propably be with a lot of leaves, If you just prune the roots and leave the tree with all the leaves intact, you will cause a disequilibrium, because now you will have to liittle roots to provide to a lot of leaves and that will make your tree to go in a state of stress.
So the best thing to do when root pruning and have leaves, is to cut leaves proportionally to the amount of roots you are prunning. If you are pruning roots like the video of Frank, maybe you should cut at least half the leaves to balance the tree. That principle applies to all trees you are root pruning, not just figs.