Brother with the old lights there was a problem with the right side light, it used to lit half. I inspected it but didn't find anything wrong with it. It was totally identical with the left one internally, bulbs were also OK. There is a sheet inside the light which picks the light from the bulb and distribute it along the whole periphery of the light/reflector same like light pipes.
Here is a picture of the old right side light (outer portion) that glows only light half.
Then I bought a another set of tail lights as mentioned in few posts above along with gaskets and back cover trims, so now it is perfect. In the picture you are referring at is glowing fully but it is the angle of the picture to make it look like that.
