I think he meant smart as in that their more apt to know what is 'cool'. It's obviously being blown out of proportion though. A comparison is with music. In high school and college everyone knows the music scene and all of the up and coming bands. It's all around you and you can't avoid it. When you're a little older it's harder to stay on top of those new artists and underground musicians.
Unless I missed a subtlety he meant "smart" as in intelligent. He later clarified that one should never compromise intelligence for experience when hiring.
