What makes groups smarter together is their love of different ideas, questions and perspectives. They know what do productively and creatively with differences.
The diveristy myth is that if we have people who don't look or sound alike, we will magically get shared competencies of generating, appreciating and optimizing differences. Years ago I got no quick or substantive answer to the question of how we are supposed to expect different people to think. How do we expect Americans or Africans, Asians or Europeans to think? How do we expect women or men, older or younger people to think? Without these competencies, even the most diverse group can get stuck or implode in division.
If we want groups to thrive on differences we need to support them with the habits to do just that.