I absolutely agree with you.
What I am saying is that moving averages work much better when you replace them with Bollinger Bands, that is, the average itself + X standard deviations. How you turn these into a trading system is a whole other deal and yes, back testing is essential. In the study you quoted, I honestly can't wrap my head around trading on a daily chart using a 5-period Bollinger Band. Daily charts imply longer maturation periods, which are not compatible with such a small average, which in turn implies some heavy volatility in terms of results.
You simply can't beat long-term results by making several short-term trades, which have much higher liquidity. It's just how the statistics work, risk is always proportional to return, liquidity, maturity and volatility. Not sure if I am making sense, I tend to post here after a few drinks.