I would be curious to see how you validated this claim and if it has more to do with the item and vendor vs cost of shipping. As a third-party vendor of Walmart, we may have an item that is sold by many other vendors but do not offer free 2nd day shipping -- the cost would reduce all profit on an item. This is similar to Amazon where certain sizes may be eligible for Prime because Amazon stocks it, but we may be the only vendor who has large but only offer Standard or Priority shipping. But if you want to know what Walmart is doing, just look at Amazon 10 years ago and assume copied services, late planning and worse integration.