I don't know, but like you said, most of them need it. At least to get proper pull up range on the trem. Guess it's difficult to mill wood to such an exact minute angle and have it be the same on every guitar.I notice that a bunch of ibanez guitars needed shims to get the neck angle right. Is this because they did not angle the neck pocket right or was it just that the tolerance allowed for such big differences? I know the warmoth bodies I have bought have the pockets milled to eliminate the need for a shim.