The summer pruning is to keep any strait up growth cleared away and keep the middle of the tree open.
A Little Note About Myself
I have always been a farm girl at heart. When I was little we had chickens and geese that I made into pets. For many years I did not have space to grow a garden or have animals so I would grow veggies in pots on my deck. Then when I had room again I may have gone a bit overboard starting out with a 3,000 sq. ft. Garden! But hey I supplied food for all branches of my family that year! :)