Are changes in balance the cause or the effect of swing tendencies? This is a difficult question to answer when we think about the all the moving parts through the different stages of a golf swing. Many times a change in balance can be the result of one swing tendency only to lead to another swing tendency in an effort to regain balance. Therefore ground reaction forces are a link between swing tendencies.
One example of this would be a golfer who stands up out of posture in the backswing and the weight goes towards the heels. When a golfer finds himself on his heels he will look to regain balance by moving towards his toes only exacerbating the over the top swing tendency of a flat backswing. Another example is a golfer who finds himself on his toes at the top as a result of a steep turn. Usually golfers in this position will stand up on the downswing as they fall back towards the heels leading to early extension or more issues with maintaining posture. In both cases the instinct to find balance can make compensatory movements become more exaggerated and lead to inconsistency.
Although balance may not always be the root cause of a certain swing tendency it will certainly play a part. Working on maintaining balance throughout the swing builds a great foundation for moving through the swing in a biomechanically efficient manner. Maintaining balance does not guarantee that posture will be maintained, but it does support the movement and provide a better chance of transitioning through the different stages of a swing smoothly. A great way to work on balance is to make swings with your eyes closed to get a better sense of how balance changes throughout the swing and to increase your awareness of your own swing tendencies.