Ross Sep 16, 2018
Many golfers don’t keep their left (front) arm straight on the backswing and hit the ball great. It is a repeatability issue. Some can bend the front arm a bit on the backswing and get it back to straight by impact and have no problems.
Yes there is tension in the backswing if done correctly. The shoulders turn around the spine and windup the back muscles. This should not affect the front arm being straight. Plus, the backswing should not be very long. It ends when the shoulders can’t turn any more. Jon Rahm is a great example of this.