From the animation aspect it is sometimes better to think of it as a parent object rather than a group of objects. Compared to more complex animation software, it is the equivalent of a bone rather than a group.
You can visually move/rotate/scale the Dummy object, move its anchor point, edit its path, keyframe it, etc, exactly the same as you would do to any other object.
You can, for example, solo it (show only the Dummy object) for animation - I don't think Photoshop has an equivalent to "show group but don't show any of it's contents".
You can build more complex hierarchical structures. For example, you can have a torso shape, a Dummy shape as a child of the torso which acts as the shoulders, and 2 arm shapes which are children of the shoulder Dummy. This enables you to animate shoulder movement (shrug, tilt, droop) without affecting the torso. Thinking of the Dummy as a group in this circumstance is a lot less intuitive to animate.