It does work like the described 'hiding' e.g. Mellow Head (for screwing around purposes only lol) with the option unchecked
http://img35.imageshack.us/img35/360...0509175826.png
and checked (no longer there)
http://img600.imageshack.us/img600/2...0509180034.png
but the exact cases when it should be used, I honestly don't know about 'em (maybe not so well documented? ...or I overlooked it). As you see I only know what it does.