If you look at the blue line in that image, it runs from the 9 on van Hecke, past the line to the right of their scorer (23). If you then run the same line (using a piece of paper) across the same position on the freeze frame from the overall footage...
The position of the camera in this case makes the person closest to the camera (Mancini) look further from the goal and less offside.
I'm pretty confident he's offside.