The problem is how he defines 'smart'. If you assume smart means you know more than an average person, it means you know a superset of the data/facts they know

The problem is how he defines 'smart'. If you assume smart means you know more than an average person, it means you know a superset of the data/facts they know, and thus you gain nothing by asking them something. However, if you assume smart means something different, like the ability to learn quickly for example, then it follows that an average person can know something useful that you don't already know, and thus you have something to gain by asking them something.