It's all made by the same few companies and then labeled according to brand.
Source: I work in grocery.
I Have seen Walmart bread come to the non-Walmart store I work in mixed with the bread for the store I work for. I Have seen name brand products come in to the store I work at for testing and after a test period are miraculously replaced with a store brand labeled variant in the exact same packaging.
The bullshit about bespoke recipes and highest quality ingredients is all bullshit. Your food all comes from the same handful of companies processed in the same plants on the same machines with packaging labels swapped out for branding.
The brand cereal is the same as the cheap cereal. The brand canned goods are the same as the store brand. The brand chicken is the same as the store chicken. The produce comes from the same farms.
The only real variance is regional distribution.