Your Parts Catalogue should show that the two studs are different in size and profile, with different part numbers. My 4.2 Parts Catalogue lists them separately.
The single stud locating to Spare Wheel Cover is much larger and part number BD. 10958.
The two studs locating the hinged extension board for the Luggage Floor are more delicate and chromed with part number BD.23717.
I attach some photos of these and for completeness and to answer your question, include the hidden clip which receives the studs of the hinged extension board, part number BD.22348. These clips are attached under the Support Rail Assembly and covered in vinyl on top where the studs pass through, so are not normally visible.
Photos taken with the cover laid alongside the raised extension board and in the second photo through the side window, so not perfectly clear, but at least you can see the difference in size and profiles.
What SNGB are offering you in your photo appears to be the larger stud for the Spare Wheel Cover.
I trust this assists,
Regards,
Dave