Yes you may be right Oni, I'm no expert, I just remember doing that sort of stuff from high school (bloody long time ago). I can remember my teacher telling us to think of a bolt being undone with a spanner, the force moment is provided by the nut and the moment arm is from the nut to the end of the lever (spanner). So the moment arm pivots around it creating leverage ie hips go back, knees go forward but bar stays central to foot position.
Thus the body has 3 moment arms, but only one force moment provided by the bar.
I suppose it depends which end you technically consider the force being applied. In your way of thinking the leverage gets harder the further away from the hips (your moment force, or central pivot point) and leveraged from there to the end of the spine (shoulders where bar is placed, low being closer or high slightly further away again). My way of thinking is the bar on your shoulders stays central in its movement (ie stays central all the way up and down in the movement if squat is done correctly) so the moment arms lever from its center. I say this because the load applied to the hips is greater when standing than at the bottom of the squat as gravity wants weight to drop straight down, hence the bar being central.
I can understand the hips are loaded more than any other part of the body in the movement, but force is not load although it can technically be load also.
EDIT: Fwaaaark that's my understanding of it anyway......well that's at least why I thought what I thought, but as I said, you may be right, not arguing with you just stating why I think you were wrong. The pic you show doesn't take account of all the bodies levers, only 1 and is talking of only 1 pivot point, which makes it technically incorrect but very understandable anyway as I know what is trying to be said.