As Mr. Jurik noticed: "A smooth (low noise) trend is more efficient than a noisy trend. Given that RSX measures market trend direction and efficiency, it stands to reason that RSX would respond better (display larger dynamic range) when fed pre-smoothed price data. And there's no better way to pre-smooth than by using JMA".
And as the result: "it reverses with the market, showing almost no lag".
Jurik's RSX is a "noise free" version of RSI, with no added lag.