I think he means to use it just for the sake of figuring out the cam timing events turning the engine over by hand, not necessarily leave it on the damper permanently to use when the engine is running. It would save the hassle of removing the pulleys and crank bolt to attach a degree wheel.
If I need to work with a stock damper and I'm trying to figure out my full ignition advance curve I'll use a tiny Dremel cutoff wheel and carefully mark the damper in 10-degree increments up to 50 or 60 degrees BTDC. Totally permanent and costs nothing.