The reason, I guess, is that if it were not so, the King could position itself next to the centre square and never be captured, even if it couldn't escape that way as the requirement is to place pieces on all 4 sides.
(gem) Træt af at skulle klikke dig igennem 2-3 side for at komme til den samme side. Betalende medlemmer kan tilføje det til deres kontekst menu. (pauloaguia) (vis alle tips)