Note this same logic holds for oxygen. This expands our ability to positively identify life to places that may not have gone the oxygen route. (We know this is possible, because Earth itself was like that for a while, and we continue to have a wide variety of anaerobic organisms, and even some complete anaerobic biomes underground, I believe.) It does nothing to our ability to negatively identify life (or positively identify lack of life, if you like), which we have little ability to do in general.
(Although it is harder to imagine life without chiral molecules than life without carbon molecules.)
