Cutting planes in a Voronoi operation are formed between points in the point cloud....so it doesn't really make sense to orient them to particles because no single particle is assigned to a single cutting plane. The normal of each plane is the vector between two given particles....so the orientation of the planes is dependent on each pair of particle's position.
However, you can use the normal scale settings to bias this direction in a particular direction.
However, you can use the normal scale settings to bias this direction in a particular direction.