Your forarms should rotate, yes. "Always point down the target line" is a bit ambiguous. Without seeing your actual positions I would hesitate to be so diffinitive...there are several other positions that can be unique to your personal swing that needs to be see first. I personnaly like to see the back of the left hand facing the target at impact, but it is a dynamic movement that as the arms rotate naturally because the lower body and torso lead, this creates all the power needed, and should not need any forced action.