ALL of the plants energy to grow flowers is made by/in the leaves.
Quite simply...........
Less leaves = less energy being made = less potential growth.
Buds do not need direct light to grow, they need leaves making energy to grow.
Light penetrates upper leaves to strike lower sites anyhow.
Energy does not get "pulled away" from anywhere, all energy is distributed evenly throughout the entire plant to where growth is occurring and it can not be "concentrated" to any particular area either.
"Lollipopping" the lower sections of the branches can be a good idea, but it is not necessary and it will not make the upper buds grow any larger than their genetics are programmed to be.
I have never defoliated any plants for over 35 years now and my plants grow huge flowers.