For the buds to grow, you need the leaves to make the energy needed for bud growth.
Just remember -
Less leaves = less energy being made = less (bud) growth!
All of the plants energy to grow is made in/by the leaves, less leaves, less potential growth.........it really is that simple.
Unless you are having MAJOR issues controlling humidity levels, I would advise against defoliating at all.
There is no energy to grow that is made by the roots or any other part of the plant, 100% of the plants energy to grow comes from the leaves and you can not remove leaves to encourage buds to grow, it just does not work like that.
Besides, if your plant would not NEED those leaves, it would not grow them in the first place!
Defoliation must be one of the most misunderstood theories when it comes to growing plants and most people do it "just because" without even realizing/knowing how plants function or the actual role leaves play in the plants overall health and well being.