In logic, discussions of a necessary concomitant often investigate strong conceptual or inferential relations. Bayān additionally asks how a speaker leads an audience from an expression's first meaning to another intended sense.
Thus “abundant ashes” evokes generosity against a particular customary background and through intermediate clues. The inference is not a timeless mathematical entailment available without context to every listener; its strength lies in linguistic and customary association.
The vocabulary of necessity is shared, but the nature of the connection, the audience's competence, and the contribution of context must be established before equating the two technical uses.