1
Yes,
W-L does provide some unique information. It provides the one piece of information that implies "perfection". The ERA, xFIP, WAR, WPA, etc., would not (by their nature) alert a viewer to any level of "perfection" - unless the ERA or xFIP were to actually reach 0.00. (And the irony here is that even with a 0.00 ERA, one can actually still lose.
Mind you - the information reveals "something" unique. But, how one would choose to interpret that data could lead in a lot of different directions.
19-5; 1.27 in 2011
24-0: 1.27 in 2013
Maybe you look at those two seasons and conclude he was just lucky in 2013. Maybe you conclude he was unlucky in 2011.
But, end result - in 2013 - he NEVER lost.