The match rules for this match tracked the rules for a military silhouette match that is also shot at this range. That match involves chicken, pig, turkey and ram silhouettes shot at distances of 220, 330, 420 and 550 yards.
The silhouette match started out "as issued, iron sight" and eventually a class of scoped military rifles (As issued sniper, as well as vintage rifles with modern scopes) was created.
The long range military match tracks these rules. Besides, hardly seems fair to pit iron sights against scoped, even if the scoped rifles are "as issued".