You can’t use Region3 on rotated parts, because Region3s are only calculated given 2 points in the workspace and nothing else. Use the ZonesPlus API instead.
Try to point with both of your hands, pretend that those points are min and max, and imagine those points on opposite positions of a cube. It won’t make sense to rotate it, but if it’s only facing one direction then you’ll be able to understand why this is the case.