Everyone looks at it from their own bubble. Someone growing in soil indoors with a small light source can get away with a single well timed defoliation because the pace of leaf growth allows it. Another person growing in hydro with a big lamp and full on climate control is probably going to need to do it a couple of times because growth is so fast. Outside growers have 4 times the light penetration, so they don`t worry about bud shading...but they should consider some defoliation to mitigate pests and fungus.
I look outside the weed community for info as much as I can and I look to nature. Tomato growers defoliate and they do it to make $$$, so by extension, we should at least be experimenting with the practice. In nature, cannabis plants are constantly stripped of leaves by critters, strong wind and insects, and they have built in response mechanisms to compensate, so why not trigger them.