Gardener! Haven't seen you around in a while. Glad you're posting again.
Interesting recipe. Seems very odd to me to mix cake flour (low protein) and bread flour (high protein) in the same recipe. I bet mixing the two gives you a protein content similar to ordinary all-purpose flour -- but then the recipe wouldn't be "sophisticated" enough.
Rob - the unsalted butter + salt doesn't surprise me. Salted butter brands differ in their salt content level, so this lets the cook control it better. Of course if someone makes the recipe with salted butter and omits or reduces the added salt, it's not the end of the world and I bet the cookies will still be great.