When I just practice the positions I keep my lead wrist 'flat'. In a real swing with short irons and wedges (more vertical swing), my lead wrist was tending to breakdown whenever I 'tried hard' (likely incorrect right arm participation). USING trail arm retention helps insure that I don't extend my right arm and having that dynamic pressure 'bow' my lead wrist helps insure that any incorrect trail arm participation will effect direction and NOT distance sinc my lead arm will rotate instead of suffering the higher effective loft of lead wrist break down.
