Necessity has a parallel scope distinction:
«لا بالضرورة»
Not necessarily — denial of the necessity of the predication.
«بالضرورة لا»
Necessarily not — a necessary denial of the predicate.
“Being a writer is not necessary for humans” does not entail “It is necessary that humans not write.” The first is consistent with actual writers; the second would exclude writing altogether.
Existential non-necessity requires denial of necessity, not the necessity of negation. Translation must preserve this difference.