Oso,
There's a lot of nuances to needle pulling. Quite frankly, I never understood the benefits until I studied at Boon's.
Depending on the situation, you may want to pull needles in the fall. Or, maybe at reporting time, just before buds open. Or, maybe when we decandle in the summer! Or all three! Or, none of the above!
It all depends on what stage the tree is in, how strong it is, what the short term goals are, etc.
I'll repeat the general principle for those new to pulling needles on JBP. Needle pulling is a way to balance the energy as displayed by foliage growth by the tree. JBP tend to want to grow tall, and put their efforts in the top part of the tree. So, usually, the strongest foliage growth is up top.
We want to have the tree appear "balanced". That is, the tree appear to be equally strong everywhere. It's impossible to strengthen parts of the tree. When we fertilize, it strengthens the whole tree. And we don't want to try to withhold light.
So, we use needle pulling. Pulling needles weakens the tree where the needles were pulled. Pull them everywhere, you weaken the whole tree. Selectively pull more from one section or another, you weaken the pulled area. So, we pull more from the strongest area to match the weakest area. Then the tree is "balanced".
This is an ongoing thing. At first, the strongest areas will continue to be stronger for several years. Over time, needle pulling, applied consistently will eventually train the tree to remain balanced, or at least be less unbalanced in its growth habits.
On a highly refined tree, needle pulling can be quite tedious and time consuming! Especially if you have to count pairs!