The scare quotes are there because the way to objectively define states of matter is by a discontinuity on a particular graph, and this discontinuity shows that there are dozens if not hundreds of states of matter. (Update: when someone says 'fourth' or 'fifth' state of matter found, you should laugh at them.)
Regardless, sand dynamics are actually quite pretty.
The problem the physicists are having is that they don't truly understand what a states of matter are - if I asked one "What is a 'liquid?'" they wouldn't have an answer that really defines a liquid. If they did, they could simply look at the sand dynamic equations and say, "Ah, this part looks like a liquid, and this part looks more like a solid," or see edge cases where some solid properties and some liquid properties are present simultaneously. Moreover, defining this thing would likely clarify what, exactly, a 'state' of matter actually is.
Do you also think that the way the falling sand grains bead up looks awfully similar to the way stars bead up together?