The Mover Path item has a Closed Loop toggle that changes whether the spline path loops back to the start, but the Mover Train has this forced always on, which feels a bit limiting and also makes spline editing feel a lot more clunky than it should since the bit of track that loops back to the start always gets in the way.
I don’t know if the Closed Loop toggle wasn’t added because of some limitation of how Mover Trains work, but at the very least it would help to have a way to hide the piece of track that loops back while editing splines if adding the toggle isn’t possible.