I think 5-year periods are not adequate. The correct period should be the length of economic cycles, e.g. 2000-2007 or 2007-20017.

This metric also makes no sense, if a manager achieved the return of the respective index or a bit more but significanty reduced the volatilty and drawdowns during crises, e.g. halving it. Even though most investors would prefer that, this skill is not reflected in this metric, as it would calculate values much below 1.

What is the use of applying such metrics to backtests such as with the MF indices here? In see no value at all except for their promotion. Because the highest hurdle for active management is to keep up its edge when market inefficiencies, which it tries to exploit, are eroded by overcrowding. This mechanism is completely absent in backtests. They are over-optimized to deliver such virtual results in the first place! However, no skill, which is discussed here, is involved.