Did you see the video on how the picture was generated? The picture shows a composite of pics taken at the center of sphere. As if you could put a rotating, spinning camera in the inside of a beach ball and have it take pictures of the inside of the ball. Then open the sphere to show the shape you see.
It's not that the satellite has left the Universe, turned around and took the picture.
I completely understand that. By definition the satellite could not leave the universe and turn around for a snap. The oval-shaped sphere obviously represents the limited area from which the satellite can gather light (in a given period of time).
However, the question of what the universe is expanding into is still reasonable.