None of the LE devices in the 747s are slotted. they are simple devices which just increase the camber. I suspect the designers went for the more basic Kugers on the inboard sections because that section of the wing is already heavily cambered. The flatter outer parts of the wing benefit from the greater camber given by the variable camber devices.
These are not the same as the Airbus LE devices which are slotted slats and vary position with different flap settings.