I can only theorize.
In altering your hook on the string to include more tension on the ring finger, you maybe lessoning the tension in your forearm mainly because you are more confident in the stability of the hook.
This may not be the best way to hook the string however. Most of the tension should be on the middle finger, secondly the index finger, and the ring finger is really only along for the ride (around 10% hold). Try to keep a flat hand with as little tension in the forearm, back of hand and fingers as possible.