What those diagrams aren't showing is that the later agitator with the "shark fins" is smaller in diameter at the base.
So for an equivalent amount of rotation, the outer edge of the fins moves a smaller distance on the newer agitator. It also, by being smaller, provides more free space for the clothes at the bottom to move around in. The two of those combine to make it more gentile on clothes - countering some of the effects of the more rapid short-stroke agitation of the newer transmission.