If your body is smaller your head is larger proportionally thus the muscle density minimum would have to be a bit higher than a person of average height, neck muscles are inefficient over greater lengths because the higher center of gravity over the center of the trapezius muscles reduce structural efficiency of the muscle, which would also be true of other neck muscles and thus a higher muscle density and greater tension pulling on the base of the skull of taller people. these aren't massive differences but it's cumulative enough that skull shape aught to be a bit different over a lifetime.