(Maybe a litte veer)
Went to Purdey a year ago for a fitting and to order a shotgun. In the wood selection, he said the desired cuts of the Turkish walnut are right where the roots meet the lowest part of the trunk. That junction is where you’ll get the nicest looking patterns and colors for the aft/widest part of the stock. For strength as you move forward and especially in the area of the receiver, the grain should be straight and parallel to the bore, which is from the trunk part of the wood cut.
Hope I understood him correctly; at least that’s the wood pattern type I picked. FWIW.