You're Correct!

Rotating the shoulders on the back swing is something every golfer is aware of but many arent aware how or why they do it. Many even swing too short on the back swing because they feel they cant make their back swing longer due to poor flexibility, however, the reason is generally poor posture.

A player with rounded shoulders at address may struggle to make a full rotation during the back swing, therefore reaching a full swing is difficult. Rounded shoulders can also cause the body to laterally move to the right side so the player can feel as though the back swing is longer. Getting out of position during the back swing can cause some severe consequences for the down swing resulting in fat or topped shots.

At set up, it is vitally important that the player has a good posture position. The chin needs to be up and away from the chest, the back straight, a good angle created at the hips and a small knee flex. The idea of the back swing is to coil up the body to create power through rotation on the down swing. The posture position will allow the left shoulder to go under the chin during the back swing and help create a 90 degree rotation without laterally moving or bending the left arm.

The hips will be able to rotate approximately 45 degrees to the top of the swing. This difference between shoulders and hips creates tension and a build up of power for the swing to uncoil through to impact but it cannot uncoil correctly or powerfully if the posture is lost.

Many players get to the top of the swing with poor posture and attack the ball with a steep and out to in swing path due to the arms leading. This means the posture will be lost as the head will have to dip into the ball, sacrificing power but also control and accuracy in the swing and shots.

The spine angle is a key area of the fundamentals in golf as it helps keep a players height and aids the rotation of the shoulders. If a player tries too hard to maintain the spine angle then they will invariably stop moving the body at all and swing with just their arms. It is important to get good set up fundamentals and then use this powerful position to help the body rotate fully.

The spine will not necessarily affect the swings angle of attack into the ball, unless the posture beforehand made this change. It depends on the players height and movements during the golf swing to how the club approached the ball. The spine angle will just assist the rotation during the swing.

A maintained spine angle during the golf swing will not cause a slice, however, the initiation from the top of the swing to the down swing with the hips and shoulders could lead to a strike but this focus should be on swing path and not the spine angle. The spine angle makes it possible to make a strong rotation with hips and shoulders.