It's kind of useless arguing with me since I shouldn't be putting words in the mouth of Ethan Siegel, and arguing on whether it is appropriate to call dark matter tiny really has no bearing on what I'm telling you about God and the Universe. But just in case you find it a pleasure to discuss these fine points with me, the very notion of mass distributed over volume involves statistics, and as you know, you can make statistics tell any story.
Consider this figure that I just randomly found so I don't have to draw one myself. You can see that the two clouds of green dots span about the same space. But the cloud on the right is more concentrated than the cloud on the left. You can imagine a third figure where there are several clumps of dots and still has the same overall space and density. Do you count the space between the dots as occupancy? Do you impose some form of density threshold to eliminate spaces that are simply too sparse? Not to mention that an atom consisting of a dense nucleus and a cloud of electrons is really more than 99.999% of space.
I'm not saying your Wikipedia references are wrong; they want to paint a picture illustrating the pervasiveness of dark matter, but Ethan Siegel is also entitled to say the amount is tiny. Tininess is really in the eyes of the beholder.