Earlier quoted context omitted.
I'm super suspicious of research like that for a couple of reasons. One it would it be impossible to publish research that came to the opposite conclusion. Imagine seeing a headline that said "replacing female and black executive leadership with old white dudes increases profit" by McKinsey. Second the magnitude of the impact seems insane. This seems larger than the difference most studies find between good leadershi…
The issue a non-diverse team will hit is getting blind-sided by lack of perspective on emerging phenomena. Given that aspect, I don't find it surprising that the benefits from a diverse team could exceed the benefits between the difference in average and good leadership. Both an average and a good leader will drown the same army if they lead them into a swamp because they've never seen a swamp before.
A black woman, a white man, and Asian woman who all graduated from Harvard and worked for McKinsey try to reduce car part inventory through logistical innovation.
I wouldn't be surprised if the more diverse group came up with a better solution.
To take your contrived example regional diversity will have a much larger impact on making sure someone has encountered a swamp than racial diversity.
I think it's easy to overestimate the effect of racial diversity and underestimate the effect of other types of diversities on problem solving style because one is so easy to see.