Nikon's models are, in order of quality and price, lowest to highest, Prostaff, Buckmaster, Monarch, and Gold.
With the Leupold, it's Rifleman, VXI, VXII, VXIII, LPS.
I don't think Walmart would sell the higher quality models such as the monarchs and VXIII, but I could be wrong. I just think that they would sell the lower quality models such as the Prostaff, Rifleman, and VXI.
So to answer your question, if there are scopes that say Nikon or Leupold, then they are in fact made by those companies, although Walmart may simply carry the less expensive models.
Zachary