Having started all this, I guess I should throw in my 2-cents worth.
I'm not used to seeing wire nutted connections, but I would guess that the longer (top) connection was pre-twisted. I can't see the actual Cu-Cu connection too clearly, but I'm going on the twists farther back along the insulated part of the wires.
Back to the definition of back-wired:
I've never seen the terminations on one of your GFI recepts. so I'm still a little unsure on this point.
I do have a box full of U.S. fittings here, including several hospital-grade 5-15 singles. It appears that if a wire is clamped on one side of the screw, it can emerge straight back or be bent out to the side. To fit under the plate on the other side, though, it would have to be put in through a hole in the rear of the molding.
I figured it must be something to do with this, but now I'm confused.
