I think it is figure 8 because that technique was a country and bluegrass standard in use for years with ribbon mics, and because the two singers are so obviously 180 degrees apart, facing the side of the capsule that would be right for a figure 8. If it was an omni, their positioning could be anything. That doesn't mean it isn't possible, but figure 8 was used in Nashville this way all the time for many years.-Richie