Thats because they are not the original super spec mounts, they were a round bar that passed through the shocker lower bush and had 2 flat ends that bolted to the wishbone, the slot was required for bottom of the shock to clear the wishbone.
The line of holes is so the position can be changed, only 2 bolts were used with the original mounts. the general advice on here is to mount as close to the hub as possible.
I would mount the plates you have on top so the bolts only see a shear stress and are not taking any load. but it might be easier to mount the way you have them, if they were on top you might have to compress the springs? depending on what length springs you are using.
Steve