As a person with allergies to specific foods, then don't make this mistake. Measure twice, cut once. These rules were written in blood, and tiniest violin for companies who fail it.
Yeah I guess a solution that reduces food waste while also being safe for people with milk allergies and intolerances would be to slap a big ass "contains milk" sticker on the label, maybe covering up the barcode so that 1) it can't be sold without the sticker, and 2) they can sell it at a discount. But that's probably bad for costco's image or whatever
It isn't over nothing, though. Allergen information was missing.
Sure, it seems silly in this case, but not enforcing it also leaves wiggle-room that you really don't want for food labelling, otherwise companies could just start leaving stuff out of it because it's "obvious".
No-one with a nut allergy wants to be unexpectedly landed in the morgue because the company didn't put "contains cashews" in the label for their satay, since it's obvious, as nearly every satay sauce on the market contains cashews.
If I were a customer who purchased this, I would just ignore it. I assume many will do the same. It isn't worth dealing with if it isn't an issue for you.