They're just trying to create some vorticity so that in the event an updraft forms right under the computer, they'll get a very nice rotating thunderstorm. Great for cooling!
Not so great for RAM clearance. It would be preferred to mount it this way since it's much easier. I spent hours trying to mount this thing horizontally in my case due to it being so big and having a fan right above it, I didn't have any room to hook on the fan wire to the tower. I had to use sewing thread to hook the inner one on. I'm never taking that thing apart again.
