looney
32 Cal
More likely they didn't want someone during the small game season with a large caliber ball that could be used to take big game.Sounds like you could still hunt small game with your .62 smoothrifle using shot.
You didn't mention if they have any rules for shotguns for large game. Many states allow it with a single projectile, but not with shot.
Disallowing large single projectile use from a smoothbore/shotgun for small game probably has something to do with a perceived lack of accuracy. They have to regulate to the lowest common denominator.