I looked at a few graphics programs and see that both Pages and Autodesk Graphic only use Center and Middle. Center means to align them on the same vertical axis one above the other. Middle means to align them on the same horizontal axis next to each other. Canvas uses Center Vertically to align on the vertical axis above each other and Center Horizontally is on the same horizontal axis next to each other.
Panorama is the only one to actually give the icon view so it is pretty obvious to know which to choose. I personally have no problem with any terminology as long as the icons are retained.