You're Correct!

The distance that you stand away from the golf ball, effects the angle that you swing the club head around you on, or your swing plane.

You need to stand a suitable distance away from the golf ball, so that you are able to keep your back straight and tilt forward from your hips enough so that your arms hang directly under your shoulders and free from your body. If you hold the club with your arms and spine in this posture position, where the club head touches the ground is the correct distance that the ball should be set away from you.

If you stand further away from the golf ball, you will tilt your spine forward too much towards the golf ball and begin to stretch your arms too far away from your body in an attempt to "reach" the golf ball. Doing this will now set the angle of the shaft of the golf club too low to the ground, or much flatter than usual and as a result you will swing the club head on a much flatter, lower, angle around your body.

Standing further away from the golf ball produces a flatter golf swing. If you wanted to produce a more upright golf swing you would need to stand closer to the golf ball. The smaller distance between your body and the golf ball will mean that you have to set the club at a more upright shaft angle to fit it between yourself and the golf ball. To produce a more upright swing, stand closer to the ball, not further away.

Standing further away from the golf ball will definitely have an effect on your golf swing as the angle that the shaft of the club is addressing the golf ball at is effected by the distance that you are standing from the golf ball. The further you stand away from the ball, the lower and flatter the shaft of the golf club is set in your address position and as a result it will produce a lower and flatter movement in the club head as you swing it around you.

Standing too far from the golf ball with your knees straight will create a feeling of reaching and a sense of lack of balance and should certainly be avoided. Straightening your legs will not create a significant impact on your swing plane.