Most of the time, fuse boxes will be the same no matter what equipment it actually has (LS vs LT). This is a cost saving measure for manufacturers. However, if you look inside the slot, it may not have a connector on one side of the fuse, which would have the corresponding wire to power that circuit. Same deal for the under hood fuse box, for example, you have no fogs, there is no fuse or relay for them and the connectors would be missing inside. Sometimes wiring will be there but the corresponding accessory, fuse and relay will not.
Maybe the PO put a fuse there as a spare.