The same is true of Amazon, but in Amazon's case it doesn't make a difference because of inventory commingling. It looks like Walmart just launched its third-party fulfillment service a few months ago [0], but if they don't explicitly commit to not commingling inventory with third-party sellers, they'll have all the same issues as Amazon.

[0] https://www.supplychaindive.com/news/walmart-ecommerce-fulfi...