Lich Changes: Stoneform Amulet

While I understand almost all changes to liches and way phylacteries work and stuff. I am curious why something like stoneform amulet would be changed so liches cant use it? Stoneskin still works and as far as I can tell from my understanding of liches they still have flesh its merely just not quite as "healthy" :P Kinda sucks to get a hold of something unique that is so acitvely sought out and hard as hell to get and then be let down in such a manner. Talk about a mood killer