Interesting. I was told Hawaii Costco's had stopped allowing obvious abusive returns like that. Maybe things have changed? But note the main person speaking in the article is a customer at Costco, not an employee, and certainly not a Refund Clerk. He didn't comment how many of those people walked back out still carrying the items they were returning.
I know from what I've seen in my warehouse, each refund is handled as a separate thing, on a case-by-case basis. I've heard the Refund Clerk say, "I'm sorry, but you won't be getting a refund today" at times, and at other times they've refunded something that completely surprised me. (The nine-year-old rusted-out generator that had clearly been used outdoors comes to mind. I was told the customer was a HUGE shopper, and they did it to keep him as a satisfied customer. In the long run, it amortized out.)
Yes, the half bottles of Vodka and such are also returned. People do it a lot, and some of them have no moral character. The expensive cuts of meat that went unused, returned after a holiday, are what gripes me the most. The look of shock on the customer's face as the clerk turns and drops it in the garbage can always seems to get their attention. "Wait! If I'd known you were going to just throw it away, I would have kept it!" "Well, sorry, would YOU want to buy a piece of returned meat that had been sold to someone else, transported and stored in who-knows-what fashion, and then returned on a hot Summer day in 90-degree heat? I know I wouldn't!"
Costco is a good corporation, that tries to do right by their membership. As in all things, YMMV.
Dave