Grasa,
I believe it is a) the nature of the tree coupled with b) selecting strong shoots and c) providing a structure/framework for those shoots to grow upwards. The nature of Smith seems to fit this Japanese growing method. What are variety you trying to espalier?
If I had given this a bit more thought or even if I could have remembered, then I definitely had enough shoots on both sides of the trunk to attempt some of the U-shape. I had candelabra in my head.f they grow back, I will keep them.
Addressing your point directly and more wordy: I am not sure this matters because I believe that you are growing in ground, right? Nonetheless, the nodes on this particular Smith tree are spaced about 1-1.5" apart and I rub off to maintain a 3-4" spacing. I have also found that both well-cared for and even neglected trees in pots regular water and nutrients of mine (specifically Bealle, Black Madeira, Hardy Chicago, Kilmartin Celeste, MVSB, Smith, Socorro Black, and Stallion Unknown) grow more quickly than the trees planted in the ground. As a result, the internodal spacing is greater in the potted trees.