Yes, fine feeder roots is what we want in bonsai pots, no argument there from me. However, in order to obtain the growth we need to thicken branches, trunks, and to heal those chop and pruning scars you need free root growth which can not be accomplished by pruning roots every year....the energy goes to healing roots and creating the resulting fine roots and not into the upper growth.
The one years growth shown above is fine and is to be expected with any plant that is throwing out shoots, a plant would die if it didn't do so. But, once again, in order for those shoots to thicken and the scars on that tree to heal, you'll need more than just year old shoots and you certainly do not want to prune these shoots in order to start inducing ramification, that would defeat the purpose of letting them grow.
Now, I am not saying this tree wouldn't achieve the growth needed to thicken the branches and heal the scars in a bonsai pot, I am saying it will take much longer to do so, maybe too long.
I agree with Dale that creating fine roots and getting the plant acclimated is important and should be done, but you do not have to sacrifice growth in order to do so. Planting in a screen sided planter that is a few sizes larger than these pots will both allow free root growth while air pruning them at the edges and by default, create the fine feeder roots needed for the eventual move into a bonsai pot. Even a flat box could do the job, just not as well in my opinion.
I also agree that ground growth or large pot growth would destroy the branching, this is true, which is exactly why we should get the growth and healing done first and only then move it into a smaller pot to control growth while starting branch refinement. Trying to accomplish both at the same time is self defeating.
It has been my experience that chop scars virtually never heal when the tree is in a small container. Even the inch or two quoted as being room enough for the roots to grow is not quite true, a healthy plant will fill that space within a year and then one would have to allow the roots to circle to achieve the growth needed to thicken the top, defeating the fine feeder roots that already exist.
Am I off track here?
Will