The last team I worked on had 2 Englishmen, 5 Indians, 2 Pakistanis, a Frenchman, a Portuguese, a Greek, an Australian, and a Kazakh. It was chaos. No one understood each other, and so heated arguments were the norm. This was not higher performance.
Presumably any benefits gained from diversity can very easily be lost in the mix of language and true cultural barriers. In the spirit of the article it'd be more relevant if it were a mix of genders, races, and socioeconomic standing at birth than a mix of different nationalities, languages, and workplace customs.
