Does anybody actually believe that diverse cultural backgrounds are at all relevant to ideas about programming language design or compiler programming? Claims that diversity is good for project organization sound believable, but I see no reason to think the diversity of background has any impact on technical contributions.

There is no moral obligation to have a diverse group, just to have a group that is tolerant of diversity, in the interest of fairness for members of minority groups. Encouraging actual diversity is just a strategy to avoid letting people who don't care about this stuff develop bubbles of intolerance in homogenous bubbles where intolerance isn't challenged regularly. The presence of diversity indicates a lack of intolerance, but a group consisting entirely of one demographic could be just as tolerant, and its homogeneity just a coincidence or a result of lack of advertising. So I find it a little strange when a group is "congratulated" on its diversity.