This is a better YouTube video describing granular physics and shows the speed (amplitude) of vibrations can cause counterintuitive arrangements of particles.
At lower speeds you get something akin to Newtonian gravity but at higher velocities you get something resembling MOND gravity where galaxies clusters and large voids appear - no dark matter needed.
Thanks for the link, very interesting. I'll have to check out the paper but just watching the video it seems all these counter intuitive effects can be described from the oscillations being related to the size of the chamber.
For example if I were to roll the chamber at a very low frequency, I would expect the particles to clump on one side, then the other and so on. This is not really so surprising and the frequency will depend on the chamber dimensions.