The long and the short of De Morgan's Laws

Well you have two mechanisms, one for selecting from a temp collection, and the rules of "not" that take  the complement within a temp collection. But this is not sets of elements, but temp collections of labels of individual narratives.

De Morgan's Law, aside from its use of the law of the excluded middle, devolves to the observation that "A or B" encompasses a full row and full column of the table. Leaving a single square as its complement.

Aside from that, negating "A or B" gives the complement: A*, B*.