A hogs heart is farther forward and if you had got the leg and the heart he wouldn't have been quite as mobile.
At most, it is a couple inches farther forward, not 6". He hit the heart and had to do so by aiming further back because the hog was quartered way. If he would have shot 6" farther forward, he might have hit the leg, but would have missed the heart and potentially the lungs as well. He could not aim at the outside broadside shot location because the hog wasn't broadside.
You can't just arbitrarily say that you need to hit in X location without taking into account actual trajectory through the body. The goal isn't to hit a spot outside of the hog, but inside of the hog. Given that hogs are not always perfectly broadside to make a heart shot, one must correct the aiming point accordingly.
So ATCDocktor's and his buddy's shots look too far back, but not when you look at the exit wounds. That the exits were further foward indicates the animal was quartered away and apparently quite a bit given how far back the entrances were and the heart was still hit.