Nah. An off center hit may pierce a heart or lung more easily than a center hit, depending on where the arrow enters. Also, hitting a limb, an arrow may or may not more easily severe a major nerve or artery and cause more damage that way, as opposed to entering directly to the center of mass and hitting a femur bone or something.
So, according to realism, I disagree.
Hitting a toe is 70%, calf is 85%.
One thing I am confused about is why arrow 5 would give such a drastic reduction of damage. Wouldn't something like matching the angle of the arrow to the normal vector of the surface at that point make sense as some sort of penetration factor?