If you see that on a product, you'd expect that the thing was made with milk, but does not contain any as far as you need to worry about allergens, and that it's tested to be safe.

It's a valid case in the truth table where somebody with a milk allergy should be safe to eat it

You will find that even butter often does not have milk in the ingredients list. E.g. Kerrygold: "pasteurized cream, salt"

In this case, the Kirkland's listed "sweet cream" and not milk.