The Profoto website lists the Magnum as having a diameter of only 13.58 inches. So I can't see how it could ever be considered as a pretty big softbox. Luke did say that the photog used the Magnum as a beauty dish so I just imagined that the four layers of diffusion panel was placed right over the opening of the reflector. Or did I misunderstand him?
Yeah, directly over the reflector makes little sense. Shooting through a large scrim (we have a 6'x6' strectched over a metal frame in the studio) that is several feet from the light would give a large soft box effect, of course.