I'm not sure WholeFoods and Trader Joes are good representations of grocery stores nationwide. Both are classified as "Specialty and natural food stores" and have drastically fewer stores than the supermarket chains.
Just because someone buys a grocery item from CVS does not remotely imply that CVS is their primary grocery store.
The USDA has better numbers representing the market. https://www.ers.usda.gov/topics/food-markets-prices/retailin...