The closed-end design blocks wire push-through and prevents accidental shorts at the back of the connector. The locking ramp secures the mate against vibration in free-hanging or right-angle cable exits.
Locking Ramp and Closed End — Harness Assembly Details
In a harness running through an enclosure with vibration, that ramp keeps the pair together where a friction-only IDC would walk loose. The closed end is the detail that saves a rework — no wire tail poking past the back of the housing to snag on a tie-wrap or short against a panel.