Green,
The Apache does not have the same structure of the Cobra. Even on the Cobra, the external passengers rode out in the open on top of the doors but had no harness or any way to secure themselves to the aircraft beyond holding on.
When the Apache came along...the aircrew survival vest incorporated a carabiner type link to facilitate being secured to the aircraft using the devices built into the aircraft for use during such rides. It was a simple mod to the aircraft that afforded the ability to do what has been done.
The incident under discussion here is the first I heard of troops riding into the LZ.
The fact people have ridden on the outside of a gunship before.....in no way diminishes the Courage and Dedication exemplified by the Marines being praised here.
They are to be greatly admired for what they did.