An important use of innamā is to direct attention to a truth the hearer could recognize but is not taking seriously. The speaker does not always introduce a wholly unknown proposition; the restriction may function as a pointed reminder.
A person neglecting a familiar obligation may be reminded by a focused innamā statement. The defect being addressed is then inattention rather than explicit verbal denial.
This differs from negation–exception, which may be selected when information is unknown or a false attribution needs direct exclusion.