Well, he's describing the occurence that there are obscenely smart lawyers you would never want in front of a court or certain clients because they aren't social (or inversely, so arrogant people can't relate to them). And there are smart + lazy people (I tend to think they just don't like the law). But it's the guys who can socialize, "sell" the firm and bring business that are called rainmakers, and they aren't always the top academic students.
It's a little different to take a test on a lark while buzzed than take it in a room with hundreds of other people who are competing for a handful of spots in the top law schools, all the time thinking "my whole life depends on this freaking test!!!!" I play the best golf of my life when enjoying a couple beers and bsing with longtime buddies--not giving a crap about the outcome will give you an amazing level of confidence. LOL