Dark matter is used to explain other observations - the accelerated movement of galaxy clusters, lensing of objects behind galaxies, the spatial frequency off the background radiation.
The authors have for some reason decided to leave "the amount of visible matter [is] directly related to the amount of dark matter" out of their list of possible conclusions but I suspect that if their data/methods are legitimate than that is exactly the conclusion we're going to end up with.
That isn't on the list because two of them items on their list are possible explanations for why the visible matter would be directly related to the dark matter. The fact that visible and dark matter are related is not much of a conclusion by itself.
