Look to me that they should be seperate, as there are 2 different back covers. So 2 different versions are released.
I was thinking that too; I think that back cover from the standard version is from the big box, which had the not for resale version inside.
If you look really closely you'll see that the "regular" one
http://vgcollect.com/item/5363 has a scan that appears to be from the box, while the back art on the not for resale version
http://vgcollect.com/item/21336 has elements of the DS case on it (notice the case outline around the box, and the white DS label along the top right) It could be the way the items were scanned though, so you could be right.
Also, I just realized that the back arts are different if you compare them side to side. Seems to me that one is really from the big box and one is from the actual DS case
EDIT: Also, the NFR version does not have the right front art. The "Polkewalker included" notice was only on the big box, not the DS case