Yes and No.
First, note that you can only move the slicing grid if producing less than the maximum number of slices for an axis, given the current size of your slices.
The slicing grid position is limited by the resolution of the source terrain, because it must align with a valid "pixel" for each resolution type on the terrain, in order to ensure that the slice is an exact copy of the original.
For example, if your smallest resolution is the alphamap resolution at 32 x 32, you'll be able to divide it into 2 slices on each axis that are 1/2 the size of it. If you choose to only produce one slice on the x axis, you will be able to move the slicing grid left and right, however only in incremenets that are 1/32 the size of the source terrain.