So it is best to say that if the Steelbook has the console's logo on it, that it should go into the Accessory category and if not then into the Steelbook category. It would be easier to do it that way rather than have to figure out how each and every one was sold.
This would then also include SteelBooks which come shrink-wrapped with platform-specific information but are otherwise non-discernible when opened, such as many Switch items like Pokémon Sword, seen here.
No. That entry that is linked should have its art updated to include the back where the label has the console logo. Then the entry can stay in the console accessory section.