You are correct about the movement calculation. The object has to have motion of some kind. So, you do need to have timeline in with motion in effect, even if you are not doing an animation. The big advantage is that delicate, post render retouching is not required to blur overlapping objects for still renders. Also, motion blurs in perspective are now super easy. For single frame/still images, C4 renders and composites the multiple frames for your single image result. You do have control over how many frames you want it to render for the results as well as how dynamic the blurring is. You can also control if the blurring occurs ahead of, behind or occurs in both directions the object is moving.