I hate to be "that guy" but in theee cases, it just makes more sense to have some extraneous labeling rather than have special clauses in the regulation dictating when it's obvious enough that the label can be omitted.
Keeping the rules as simple as possible reduces the chances of loopholes and ambiguity, at the expense of sometimes resulting in things like a jar of peanut butter stating "contains peanuts" on the label.
It only makes no sense until you stop and consider how to define and implement a better rule, when the only real benefit would be to prevent people snarking about milk having a "contains milk" labeling.