Already tested, and I jump into this conclusion.
You need to have the same amount of slot to swap in the same shortcut. They (slotted and nonslotted or one slotted less) have different item id.
As long as the item id for equipment same, whatever card inside it would go the same shortcut, but different amount of slot is different item id.
In the game, I don't think you'll meet this kind of problem. having 1 more slot in the same equipments is totally better, which in the end you will use the same (more) slotted equipments.