On that TC picture, the roofline and the horizontal edges of the slide run parallell as they should. The floorline of the cabover runs at an angle (I have actually copied the pic to a powerpoint slide and drew some lines to check). Since the sidewalls of the camper appear "normal" where the cabover protrudes, there is no reasonable explanation how a camper could actually exist like that...
Automatic Photo Stitch as part of a panoramic photo?
I have seen overloaded rigs like that in the wild, though... Small euro pickups with short pickup beds and long rear overhangs make this easy.