Supermarket brands tend to be a national brand rebranded with the store’s packaging.
Walmart’s Great Value peanut butter is made by Peter Pan, and their ice cream is made by Blue Bunny. Kirkland coffee is Starbucks and their batteries are Duracell, according to this article from June '22.
There are a few manufacturers in every category that make only private label brands, but most atore brands are made by very large manufacturers.
Its highly profitable for both the retailer and the manufacturer…ans the consumer wins with lower prices for things that literally roll right off the same production line
(Spent a fair amount of my working life managing private label programs in the hardware industry)
We see this over here in the UK when product recalls are issued because of a problem at one factory. Most of the supermarkets become involved because, as you suggest, they all use the same manufacturers to produce own-brand products.
Interesting! I’ve suspected a few of these pairings. I sure wish we had an Aldi in our area; not one in our tri states of WA, ID & MT. The closest TJ’s is 250 miles away in Spokane. Deprived!