The single most common writing problem shared by short story writers of all stripes is not understanding the difference between ambiguity and vagueness

In ambiguous stories, the author—and the text itself—understands things that the narrator/protagonist do not. Ambiguity involves a tactical withholding of knowledge and clarity for effect. In vague stories, the author is as much in the dark as their characters

Another way to put it would be that ambiguous stories are stories that have grappled fully with the moral and thematic complexity of their material, to finally arrive at a place of illuminating uncertainty. In vague stories, the uncertainty is unearned, a darkness