@steyin, works as expected here. Maybe your texture's pattern is deceiving you, so by shifting it looks that it also has rotated?
@John.McWaters, it works the same as in bitmap loader (or Corona bitmap) - when real world mapping is turned off, then offset is working in UV space, i.e. setting offset to 1, shifts entire texture to the same position as it would be when offset is 0 and when real world mapping is on, then texture shifting is performed in world units - setting it to 50, shifts texture by 50cm.