By me all Supertech is in WPP bottles - including conventional, high mileage and synthetic.
IIRC correctly - Supertech can be made by WPP, Mobil, SOPUS or Citgo (all have different shaped bottles and it varies depending on where you are in the US). I believe this is typical for both conventional and synthetic. Your local Walmart may have a mix of different types (i.e. 5w20 may be in WPP bottles but 5w30 is in Mobil bottles or any other combination).
It is a safe assumption IMHO that all Supertech in the Mobil, SOPUS or Citgo bottles are made by their respective manufacturer however it is UNKNOWN if the Supertech oil in the WPP containers is actually made by WPP along with the container itself or if the oil by some other manufacturer is simply bottled by WPP. However most do believe that in fact Supertech in WPP bottles is indeed made by WPP and WPP has stated they do in fact manufacturer oil for Walmart. However WPP is also a bottler and no one really can be sure it is not QS oil in a WPP container or whomever the lowest bidder is.
The important thing is is that all 5w20, 5w30 and 10w30 Supertech are API SN rated.
I have bought plenty of WPP 5w20 Supertech for older vehicles and have experienced no issues. Supertech is by far the best selling oil in my local Walmart - there is shelf space in the oil section and an entire end aisle stocked full of Supertech oil and it usually looks fairly depleted by the end of a Saturday afternoon.