The diagram is showing the ball flight laws if the body alignment, feet, hips and shoulders are square to the target line. I understand you can aim in different directions. If you aim 10 yards to the right of your target you would be better off hitting a pull draw then a push draw, it all depends on what shot you are comfortable with.
norrisedgar, The statement in bold is not correct, the dotted line is the target line/body alignment. It does not mean it is the start direct of the ball. The black arrow is the start direction and the red arrow is the path/swing direction.
The ball flight laws in the diagram are relative to the target line. If you have a hard time swinging with an outward path to hit a push draw then you can aim lets say 10 yards to the right of the target line, swing along your body alignment and hit a small pull draw to get it back to the target line. Like Erik said there are many ways to get it done.
It's more of a path issue than your grip. I have a fairly strong grip(the V's of the thumbs point to my right shoulder)and I hit the ball stright and at my target line when I am rotating my shoulders around my incline and not rotating them to level. You need to keep the head steady, rotate around your torso, keep the head behind the ball and don't force your hands to rotate through impact.