I would have to know if the "guy" was referring to a thread furled leader or a fluorocarbon furled leader. From my experience, the thread furled leader might be to limber to transmit the "tale-tale" strike like a stiffer fluorocarbon furled leader would. The thread furled leader will want to float higher and just "lose" contact with the tippet and this would cause you to miss strikes. Just my thoughts and nothing more.