Steve,
I can agree with you about the nodal spacing of 2-3 inches being an indicator of good growth, but I cannot agree about them growing at a "moderate vigor". The fig trees were provided with regular fertilizer and watered daily, I did not attempt to restrict their growth in any way, other than growing them in small containers. They grew to their optimal inherent vigor under those conditions. Several cultivars grew at a longer internode spacing under the same conditions.
One of the keys to pruning to the "Japanese Container Tree Form" is pruning the fruiting branches back to 2 buds/nodes for the growth of the current year's fruiting branches, and leaving only one shoot to produce figs at each fruiting branch. Once the main scaffold is formed, this technique forces the tree to puts all its energy into those limited branches, keeping it small and productive.