I generally don’t think of brush piles for fishing. But, have fished a lot of them in public lakes. To me, they are mostly protection from predation for small fish until they get large enough to make a meal for larger predators.
Lusk says that only 5% of the eggs laid and hatched ever survive their first birthday. So, I like the idea of different sizes of prey/groceries. This stuff is, to me, just Mama Nature at work.
I am going to, soon, cut some cedar limbs and small trees to augment my brush piles. They last about 4 years max in my area.
I don’t fish too close to them because I get hung up too badly. But, I fish somewhere in the vicinity.