Classical commentaries link the permissibility of existing unripe fruit to recognized saleable value (mal mutaqawwam)—a lawful benefit in its present or anticipated state.
A green fruit may already have lawful use, such as processing. Some Hanafi authorities also discuss its future usefulness, although jurists disagreed on cases of fruit with no present utility.
It is therefore incorrect to infer that anything wholly nonexistent or devoid of recognizable value may be sold.