Great photo and example, Paul. This is a question I keep getting, especially from advocates of One Straw Revolution, Fukuokua in Japan. I, too, have pruned old abandoned orchards and cleared out all the dead wood from the interior that died from lack of light... and can only imagine the disease and bugs that no longer could find easy homes once I was done.
A point I like to bring forward is all the energy of growing that will grow in places that will be shaded out later, that will need pruning off later, if efficacious pruning is not done in a timely manner. 6 years is a good time to put the tree/house in order for production and good health. Hear here.