Well, ady zoom the image when vader leaves at the final scene and with that way he covered the misplaced alcone/exit without showing the end of the other pylon.

if the bridge have a continuity the alcone section defines a more correct approach between shots.

If that is true then the panel that is in the middle of the path in ROTJ is correct. ( we see the same in ESB the pica above)

The matte changes the actual set so the establishing shot be more clear.

As for the floor contrast that was a stylized move lol.

-Angel