Quote - ....as if the morph changes linearly

Morphs always do change linearly, that's in their nature, and that's one of their shortcomings, the vertices in a morph always move in a straight line. And that's why morphs are useless at implementing rotations. You should be able to get away with with an eyes closed morph, because whilst in the real world the movement is rotational, the degree of rotation is very slight, and you can fake it by by linear movements. But never try to move an eyeball with  a morph, as that would move the geometry away from its joint centre (origin), and that will cause problems. For a bit more info on this last  point, see this thread.