What you said is true for their physical locations, but both Target and Walmart implemented Amazon-style marketplaces a while back, and my impression is that there's very little oversight or quality control. Even less than on Amazon.
I'm pretty sure they don't co-mingle though. So if you make sure you're buying from Walmart or Target and not some other party you should be getting the same items that are in the stores.
I'm pretty sure they don't co-mingle though. So if you make sure you're buying from Walmart or Target and not some other party you should be getting the same items that are in the stores.