I'm sort of a backyard mechanic... so I know how I would have made the patch, but I would imagine the people that made THIS repair were much more talented than me.
Here's how I see what happened.
1. they take the coaming off by drilling out the rivets. They throw it in the trash, or maybe use it to cut a piece the same size to make the patch.
2. They decide it's pretty big and it's going to bend, so they rivet 5 thin pieces of stiffeners to it, sort of evenly spaced but not really taking into consideration where those 5 stiffeners will line up on the plane.
3. They test fit it on the plane and figure out what they need to do to get it to wrap a little bit around the curvature of the plane. Up at the top they likely beat a curve into it so it would lay flat onto the surface of the plane and not leak water. In doing all this they bend and dent the piece of metal a little bit, leaving it how we see it in the pictures on the plane (a dent in the top right quadrant, a bit of a bowled, sagged effect near about the 4th row of rivets... nothing perfectly flat, kind of warped)
4. After riveting it on the plane, they notice that it's still 'oil canning' because if you press in on the center of it it bends in an inch or so... so they decide to put a stiffener inside where the original vertical piece was. They go inside the plane and cut some sort of angle iron or whatever and somehow attach it to the top where the original vertical stiffener was and then at the bottom... they may have attempted to curve or cut a relief in this piece to make it match the gentle curve of the plane. It likely touched the skin or was close to it, but that would change if the plane went airborne as the pressure and wind moved the panel in and out as the air moved over it.
5. Thinking that it was well enough for their patch job, they rolled the plane out and these pictures were taken, dent already there, bracing already there, patch already installed, etc.
I think it had a minor dent in the upper right quadrant that was there from when it was installed and beat/bent/warped into place, and there also may have been a stiffener vertically in the center of the window (where the original one was on the skin of the plane above it) kind of haphazardly almost wedged into the window frame opening or whatever remained of it on the inside of the plane.
That's how I personally would do it. If the argument is I'm not a plane mechanic and they would have done a hell of a lot better job, that's an argument I think is feasible