Playing with the difference that Les pointed out (in P6 at least), it appears that this combination of the camera’s Scaling being linked with the change in the Perspective dial, allows you to somewhat simulates the cinematographers’ “dolly/zoom” move,  i.e. zooming-in while dollying back, or the reverse, to effectively keep the foreground subject the same size in the frame while causing the background to compress or expand behind them.    A well employed example of the disorienting effect this causes is the medium-closeup of Roy Scheider in Jaws when he first sees the size of the shark.
 
Dunno if that’s what they were really going for, but it seems to work pretty well with longish lens lengths.