Well, IMO, that category is logical. Because the ship is used mostly for that slavery business, with its design fitting to that category. It's a known unlawful make ship model in the game, and in RP, the cops will catch you for simply flying that ship.
Junker ships are not necessarily unlawful.
It's not a generic civilian ship. It's a nasty unlawful ship that's built for slavery, and it marks you as a bad guy everywhere. It stands out everywhere as much as a Wraith would stand out in New York.
You shouldn't be able to fly that ship and open it to the lawful factions like for example an Eagle.