Concept of Batch Size in Scrum with Kanban

Ideally when we reduce batch size, efficiency increases. As the amount of actual work during Work in Progress is reduced or we can say through any stages in the KanBan Board. Can there be a case that reducing our batch size backfires (yes DT is not challenging itself & not progressive). Or in other words If we reduce our batch size, overall efficiency will ALWAYS increase? Appreciate your views.