Containers of shapes/fluid for rail transport are not symmetric along their long axis; when loaded on a train, the circle showing the colour/shape it contains is closer to the side which is at the "front" of the train, i.e. in the direction of travel.
Both the normal Shape Loader and the flipped/mirrored version load containers of shapes in the correct orientation. However only the *normal *Fluid Loader loads containers of fluid in the correct orientation; the flipped/mirrored Fluid Loader has the circle at the back of the container. As demonstrated with the containers of green fluid in the attached video, the containers are created and wait to be loaded with the circle at the back end, and once they're fully loaded onto the train they then snap to the correct orientation.
This is only a cosmetic issue, but the abrupt snap to the correct orientation is very eye-catching.