The secret to accurately driving a golf ball lies in what I call free-flowing motion. Tension is a swing-destroyer.
Tension can manifest itself in many ways.
The most common is in a tight grip. In the first photo, the line formed between the knuckle and the index finger on the left hand and the same line on the right hand must be parallel so both hands can work as one. When a player's hands are tight, so are the arms, shoulders and neck, causing the head to move. The body accommodates the swing. This can only happen when a player is relaxed.