Train track change up close - GIF

[Saltfever]

Agree, the skate is not moving the wheel sideways. Watch in slo-mo if you can. That tapered, pointy end of the next rail is positioned right where the skate slides off. The flange of the wheel locates (or is guided) onto the pointy rail and that transitions the wheel over to be fully on the new rail. As you suggested the skate may be used as a retarder and only one is needed.