Don't ya'll see? It IS mostly like a bookmark, but there is something special about some of these apps. They behave differently in ChromeOS. When I launch a Google app from the icon in the shelf a white line appears under the icon. Now, if I leave the window and click on the same icon again it will return me to that window.
Stitcher's icon acts like a dumb bookmark. It simply launches another instance of Stitcher in a new window every time you click on it. And there is no white line under the icon when it is running.