Why is “the crop was harvested” imprecise for inḥaṣada al-zarʿu?

Characteristics of Form VII (Infiʿāl): Intransitivity, Manifestation, Resulting Action, Equivalence, Root Restrictions and Independent Use

• Because the book means reaching harvest time
• Because al-zarʿ is a sound masculine plural
• Because inḥaṣada is an active participle
• Because al-zarʿ cannot be a subject