Not sure if this has been covered already but I thought current guidelines were for a ring socket that an earth from each cable went to each of the earth connectors on the socket ?
That's what the diagram shows in the current on site guide anyways.
In my opinion both earth conductors should go into the same terminal. Putting them in separate terminals means both screws have to be tight to ensure continuity of the earth to other sockets.
I also gently twist bare earths together inside the sleeve to further reduce the risk of loosing earth continuity if the terminal becomes loose.