Do you know if your state has WIC cards or checks? Regulations vary by state of course, but assuming cards (all states and tribal organizations are supposed to be rolled out with cards by 10/1/2020, but of course there are a few stragglers) there is at least some truth there.
Rather than just giving you money to spend on food, WIC authorizes you to purchase specified foods and then pays the store whatever the price is for that food. Under the check-based system, there was obviously a lot of slop. A WIC voucher might say "1 Gallon of whole milk, 1 jar of peanut butter, and 36 ounces of cereal". So the customer would pick out those things and hand the cashier a voucher. The amount would be printed or hand written onto the voucher, along with the vendor number and then it goes into the drawer, eventually through the banking system and the store eventually gets paid. Actually worked pretty well on aggregate, however there are some obvious holes in the system - what if the customer only bought 36 ounces of cereal? Arguments over the prevalance of this kind of thing made implementing cost-containment measures pretty difficult.
The big cost-containment measure that did get implemented a long time ago was requiring state WIC programs to solicit bids from infant formula manufacturers to be the preferred infant formula in that state - manufacturers agree to rebate a percentage of the wholesale cost of the formula to the WIC program. Absent a medical reason for something else, if you're on WIC and receiving infant formula, it will be the contract formula that is issued for your child. So figuring the amount of formula bought by WIC is a somewhat tricky analysis, but there was enough money at stake that the manufacturers and WIC programs agreed on how to do it. But still arguments come up from time to time - how do you know that check was redeemed for all 10 cans and not 7? Larger states this rebate comes to 7 or 8 figures every month, and push comes to shove, we really don't know for sure.
On top of that, the in-store shopping experience for WIC participants was not great. Cashiers had to be trained on what to do, and all the rules of the program such as WIC participants are supposed to buy the lowest-cost option of whatever it is. A certain stigma as the transaction was not like a normal grocery store purchase. Confusion at places that did not specialize in WIC customers was rampant, and they found the stores that did specialize in WIC were often charging a pretty high price to the program. So we need to contain costs, but we're somewhat limited in rules that can be implemented because the data isn't super clean, and margins being thin in grocery means there's push back on anything you try.
Enter the WIC card - solves a lot of these problems. Stigma is lower, once participants learn the way the cards work it is a much closer to a normal purchase - put your stuff on the belt, cashier rings it up, you swipe the card and enter your pin. Anything not covered can then be paid for. One really positive thing during this crisis with the cards - if a family already has a card, there is no need to deliver anything physical to them to issue further benefits. Like say a stack of paper checks for the next month's benefits. And we've got really good redemption data now.
But the core of the program has not changed - we're still not giving out cash to buy groceries with, we're issuing 10 cans of formula and so on. So the WIC program provides an approved product list to the EBT processor, who in real-time, checks the purchases against the list, the balance on the family's WIC card and approves / denies purchases. They also apply some crude cost-containment measures in real-time. If you ask $1000 for a gallon of milk, the purchase will go through, but the store will not get anywhere near $1,000.
The approved product list is basically a list of UPC or PLU codes that are divided up into categories and subcategories. Now, because WIC vendors encompass a wide range of stores - from mom and pop grocery stores to giant corporate operations like Walmart, a wide array of products wind up on the list. And the EBT systems typically do not restrict a UPC by stores in anyway. So you'll sometimes see a Great Value product bought at a store that is most decidedly not Walmart. This setup affords flexibility to participants and grocers alike - Walmart happens to be out of whatever-o's, the brand-name cheerios can be purchased without issue.
Payment is faster via the cards, less training required particularly if you've got a good cash-register system. On the whole things are much better with the cards. However, the whole "can you buy this with your WIC card" is not nearly as much at the discretion of the cashier as it used to be.
Which brings us back to the meme - if a particular product is not on that list, then a WIC customer cannot buy it right now with their card, even if they have been issued benefits in that product's category. There are ways for participants, vendors, and manufactures to submit products for consideration, but in general the approval process is not immediate. And we have been working through some problems that stem from the "cashier really cannot let a substitution happen easily" that frankly could have been dealt with a simple note in the old system - "hey let people buy the whole milk even if the voucher says lowfat if that is all you have." The overall system for the WIC cards hasn't been tested like this until the pandemic led to widespread shortages - we're finding areas to improve, but there have been some "why didn't we think of that before?" moments for sure.. You'd run into a little of this if say a hurricane hit a particular area, but even then the issues are pretty localized.
So if you see that WIC sticker on a shelf, that means that product is almost certainly on the APL - WIC participants can buy it. An absence of a sticker does necessarily mean the opposite, but it is somewhat more likely a WIC customer cannot redeem benefits for that item.