Well not only have I heard but I've seen it a # of times. Your placing a fish in a closed system that grazes on things and there is always a chance it's going to go after some thing.
The 75% fine seems to be way out of line as more than not people that have angels have some kind of pick whether it's on clams, zoo's, soft corals, sps or brains. Actually more people chose not to keep angels in their tank to start with. Some people have learned to live with it as the angel will only go after certain corals and leave everything else alone.