Walmart has been known to put pressure on brands to reduce the cost of their products. Sometimes they can find the cost savings in the economy of scale of doing business with Walmart. Sometimes they find cost savings by making a cheaper product.

Buying something from Wal-Mart is far from a seal of quality.

Same! I received a 20,000 mAh store-brand battery from WalMart a while back, and it works really well, was a good value, and can run a Pi forever. Same goes for the HDMI -> RCA adapter of theirs that I literally asked my mom to get (she's not technical, and managed to get exactly what I needed, which is great!)

Yay, WalMart! (And Best Buy, for that matter- their online pick-it-up-in-five-minutes option is amazing.)