Actually when the plant drops the leaves off it’s not to give light to the buds but more of a nutrient mobile issue. NPK nutrients are mobile and that means the plant can move them around and use them where they are needed the most. Like late in flower when you are not feeding them N for example. That forces the plant to use up stored energy so it moves N from the large fan leaves to new leaf formation or some other part of the plant that needs N. If this occurs earlier in the plants cycle it’s a sigh of a lack of one of the mobile nutrients and most of the time it’s N but not always the plant moves around. Later in its life cycle it could be P or K that the plant is moving as well. It just depends on the cycle of life the plant is in at that time.