Costco and BJ's have TVs and other electronics made just for them. Even though they have the Samsung or other brand names, the specific model numbers are unique to each chain. No doubt Walmart does the same.
Back when I sold electronics, there were "house label" brands made by major manufacturers, but that were essentially regular production units.
Radio Shack used to have their own line of police scanners. They were made at various times by Uniden, Regency/Relm, GRE, and even Whistler. There were a couple of functional and cosmetic changes, but they were the same as the producers own brands otherwise.
They did the same with stereo components and other items as well. Radio Shack never owned a factory, so they never made anything.
Some of the things people buy or bought at Sears are the same.
When VCRs were in production, there were essentially three companies that made all VHS machines. No matter what the label said, they were all made by Panasonic and two other companies. That made repair pretty easy since almost all parts, except for cosmetic ones, were interchangeable.