The contrast between exhaustive singulars and exhaustive plurals matters because a singular form can remain morphologically singular while a rule is distributed over each member of the class. A plural can present members as a plurality or collection.
FormFocusCaution
Exhaustive singularRule applies to every individualSingular does not automatically mean one identified person
Exhaustive pluralAll relevant individuals or groupsThe discourse sets the scope
The commentary illustrates why form alone is insufficient. Address, negation, exception, and customary restrictions must be considered together before classifying a usage as exhaustive.