The article states that including partnering companies in the free shipping offer is a significant risk for Walmart, giving that there is no certainty that the partners will be able to deliver and synchronize with the service. I don’t usually speak in favor of the company, but this time I think that Walmart got it right and that they wouldn't be going into this if they weren’t entirely sure that the partners could deliver the goods up to their standards. The other thing is that Walmart had to go into this now, otherwise it would be uncompetitive in the holiday season in the segment of online sales, and, therefore, would end up losing a lot of money.
https://www.fool.com/investing/2018/10/24/walmart-takes-a-big-risk-heading-into-the-holiday.aspx