It seems to me that the Line command should only order units that are actually in a line and linked (horizontal or diagonal). I have been told that this is not the case and that all units linked may be commanded, regardless of their position. This lead me to believe that theoretically a line command card could allow for someone to move their entire army at once. This seems overly powerful. Does it truly mean all linked units?
Like all cards in the game the title is only for flavour and is not rules text.
It is a subtle design that makes you pull the line together, and subtle set up changes can make it reinforce the professionalism of some armies. e.g. Rome vs barbarians where the barbarians are often in scattered groups.