This is directly from the Warranty - Necks with shafts of Rosewood, Ebony, Pau Ferro, Bocote, Ziricote, Bubinga, Purpleheart, Padouk, Goncalo Alves, Satine, Roasted Maple or Wenge do not require a hard finish.
Agree with Stratamania, Walnut is not on the list.