They are there. It takes many, many years for them to break off. fish love the last brush line off the sides of those points. Many times there will be one specific small section that was really thick. That is your irregular feature. Sometimes one larger tree will grow right out on the end of that point. I could be called a small tree and not a bush and it will hold a big fish.
Depends on the impoundment. Woody vegetation, esp those found in So-Tex - yes, agree with DH. But take tawakoni; 99% of what grew up around tawak during extended droughts just died and depleted the oxygen content in those areas. what remains is the 1% of the true brushy stuff. Each body of water has its own characteristics. Some are renown for flooded brush, others not so much.