The blade rotates, and acts like a ruler - in one direction it's stiff, and in the other direction it's quite flexible. In between is a non-linear change from stiff to flexible.
Not that I'm aware of. The loads are quite high in pushrod suspensions, with quite small deflections, so I think most cars go for stiffness in that region so that the spring is the only elastic in the suspension - makes figuring everything out a lot easier.