Thanks for posting the link. I just got around to reading it, and a lot went over my head but it sounds to me like the author found that placing the two subs to either side of the listening position was better than placing one in front of and one behind the listening position because the ear could derive spatial information better from laterally placed subs.
At some time in the future I'll have to try that lateral sub placement; for the moment it's not possible in the room that I'm using because of a doorway and a large propane heater.