I see "supply chain issues" everywhere - at the grocery store (as noted, Gatorade seems to be hit or miss, and cat food in general), at the pool supply store (seen the price of chlorine pucks recently? They've almost tripled), and in work-related stuff (certain silicon-based chips are simply not available, affecting the final assembly of circuit cards for a myriad of things, including cars/trucks). Just some examples off the top of my head.
Even though you may come across a local glut of items it doesn't mean there aren't issues elsewhere. And of course, with Costco the specific products they put out are always varying, so maybe they are just putting out everything they can get, vs what they would have preferred to get.