I didn't design that map, but I can imagine it this way: If all four territories meet at a point, would you really be able to march an entire army across that point without first entering one of the other territories? The numbers on the maps are called armies, not infinitely-thin-men.
If you think WarLight should be that realistic, then you also think Issander should remove Rockall from this map: http://warlight.net/SinglePlayer?PreviewMap=19235
This is Rockall.
Do you honestly think you could fit a whole army on there?
Therefore, either the men are infinitely thin or it's just a game so realism doesn't matter too much.
Edited 9/17/2014 22:45:09