If they wanted a grocery store could just sell that data. Discount cards guarantee that a given shopper buys their merchandise instead of another brands. Your use of they is ambiguous in this context.

Larger stores, like say Walmart or albertsons, are far more likely to have direct deals with brands. Smaller stores often will with in particular local brands bit it depends on the specifics. Your run of the mill grocer, rarer and rarer these days, probably has very little direct interaction in the way you are suggesting. It's certainly not why stores reorganize, when that is demonstrably because that just boosts sales.

Go chat with managers who do procurement at a grocery store, this isn't secretive conspiracy stuff, it's all just out there.