I dont know where your at but, over 95 % of the green veggies come from the Yuma AZ area or southern CA in the winter nationwide...Yuma is said to produce the majority.
Doesnt matter which store you purchase from.
How long it stays on display at those stores is up to that store.
I’m in PA and I suspect Walmart refrigerates them or otherwise preserves them longer than broccoli in other stores. Not my area of expertise at all, but the taste and texture are distinctly different.
And yet overall, the Walmart produce section is clean and attractive.