Lollipopping is defoliation, you are removing foliage when you lollipop. I think the bigger issue is the term in itself. And removal of branches and leaves is defoliating.I don't defoliate but I do lollipop my plants. Removing 10 or so fan leafs to minimize any popcorn buds is not going to be the end of the world.
I think that indoor you need to do some form on canopy management. Outdoor I wouldn't touch a plants leafs at all.
Some people call it selective leaf pruning whatever you want to call it. Removing some interior site blocking fan leaves is fine. And lollipopping works if you are growing for sea of green or in densely packed rooms. The light just isnt going to penetrate and get to the bottoms so no good production occurs down there.
Timing is everything. You never want to stress your plants out or remove too many leaves or like mentioned many times will screw up the plants ability to breathe and regulate co2 and oxygen etc.. I never found anything wrong with removing a few leaves here and there or lollipopping so long as it is done at the right times and for a purpose. Good growing