In that 1st article the writer states that:
Mushrooms, (actinodiscus, ricordia sp., inodiscus sp.), are the least aggressive corals.As far as I know, they have very little, if no sting at all. Part of the natural defense of mushrooms may be that they have adapted to lower light, current, and water quality than other corals can stand, so they have little competition for space.
I don't know about anyone else here, but from my experience shrooms have a VERY strong sting - when one shroom polyp landed on my brain coral the brain almost died before I realized what was happening...whereas my Frogspawn pretty much touches the brain and they seem to have come to an agreement...the brain doesn't look like it minds the frogspawn anymore.