That paper has two main points in its conclusion: Our result provides insights into the trade-off between diversity and ability. An ideal group would contain high-ability problem solvers who are diverse. and also But, as we see in the proof of the result, as the pool of problem solvers grows larger, the very best problem solvers must become similar. In the limit, the highest-ability problem solvers cannot be diverse.

Here's a paper (linked from my earlier link) that quantifies some of the benefits of diversity for problem solving. https://www.sciencemag.org/content/254/5035/1181.full.pdf and here's one that demonstrates that diverse groups get "highly nonlinear and universal increase in performance" http://www.sciencedirect.com/science/article/pii/01672789909...