Of course you have to consider the individual because no matter how overwhelming the evidence is, there will always be exceptions. This idea is easier said than done though.
A good example of that would be in trying to determine how well a player will age before giving him a contract. You can look at the individual's injury history, conditioning habits, athleticism, body type, the way he plays the games, etc. all you want, but in the end, you really can't know how that player will age until he actually ages. All you have to go on is how the group with similar characteristics have aged, and make your best educated guess.
GMs used the "Large N" idea all the time, because there is absolutely no way of predicting with any certainty what an individual will do.
Lindbergh pointed out that, despite what some want to believe, the FO did not just look at their stats and call it a day. They did consider the individual. They had conversations with Hanley to gauge his attitude and confidence, and they consulted scouts and other sources to gauge his psyche. Without having a crystal ball, that is really all any FO could do.