As part of our treestand safety classes, we (another and me) "fell" from treestands. We did this a lot, and finally made a video, which begot another video, which begot the one you see from NBEF.
I wore a standard (at that time) belt and Jack wore a Seat of the Pants harness. I KNOW what happened to me, and I SAW what happened to Jack.
At no time, ever, was Jack not able to easily turn around and reclimb the tree, using his already placed steps. And he typically continued on with his speech while he was doing so. Since he placed his tree strap high, as we taught, he was just barely below his treestand at all.
I really don't understand the premise of not being able to save yourself while wearing a safety harness (unless you are unconcious).
ChuckC