The reach being made with some real facts being added is, low income people are using the very local, on ever corner dollar general and like type stores to source their daily food from.
As such, instead of going to HEB and buying 1lb of ground beef, 1 can of tomatoes, 1 can of tomato sauce, 1 package of Spaghetti Seasoning. Having now several meals of decent quality for the $6.24 they spent, they instead stop at the corner dollar general and by a frozen pizza, or a box of Taquitos, 2 frozen burritos for about the same costs getting less value and likely less nutrition.
But that said and why I see the conclusion being made as off...I shop at HEB almost daily for our food and I see carts loaded with junk, toaster pastries not fruit, eggs, yogurt. Frozen pizza, or Taquitos, or frozen burritos, not some veggies, a meat, maybe a starch.
IOW, the location of shopping is less the issue then the desires and concern for what they buy