Sure - and postseason data is very small anyway (against good teams, which is important)
But the bottom line to me is that clutch moments are almost always decided post hoc (and really more for us fans). The players are not robots - but by and large, the guys you want up with the game on the line are the guys you'd like to have up in general. David Ortiz is the greatest clutch hitter in Sox history. But then, he also has had far, far, far more chances to deliver in big spots than any other player in Red Sox history.