This is a portion of my dock on OS X. (You’ll have to click it, since the important part is truncated by this forum).
The SketchUp icon on top was dragged into place from the Application file as a quick-launcher, just like every other icon on the dock.
However, when I click on it, it doesn’t launch itself, it opens a new instance of SketchUp on the dock, the one you see below with the dot indicator on the left. When I quit SketchUp, the bottom one disappears and the top one remains.
Obviously all the other apps on my dock behave normally, launching in place with a dot to the left to show they are running.
Really just a persistent annoyance… since I use the dock for quick app switching and their location is muscle memory for me. The SketchUp icon gets clicked a lot and nothing happens until I realize (again) that it’s somewhere on the bottom with other incidentally running apps.