The text of the law seems to be specific that the beer exemption (and other alcohol) is about a permission to put the vintage (year month, etc), since alcohol are expected to change over time even after bottling (some better some worse) so consumers would desire that information even though it does not conform to the normal "use by" or "best by" relevant to other products (any other placement or use of a date on a label being what is made illegal by the law)