I think he was talking about average in terms of talent while you seem to be thinking in terms of social norms.
The way I've seen is put is: A's hire A's and B's hire C's (couldn't find the original source of that)
Highly talented people like to hire other highly talented people. They recognize that they will learn from them and the team will be better. Average people (the B's) will often hire other average people or less talented people. Have heard it explained as they're less secure and more protective, or that their criteria is more generalized and less stringent.
The way I've seen is put is: A's hire A's and B's hire C's (couldn't find the original source of that)
Highly talented people like to hire other highly talented people. They recognize that they will learn from them and the team will be better. Average people (the B's) will often hire other average people or less talented people. Have heard it explained as they're less secure and more protective, or that their criteria is more generalized and less stringent.