Every person in the history of the world has a million unspoken, unidentified assumptions based on where and how they were born and raised. Our (early) experiences shape us profoundly, and it's impossible to overturn that even if you try.
Nobody is "neutral". It's simply impossible. Therefore, diversity.
I think this supports the statement you are responding too. The million factors impart a diversity of perspective regardless of whether there is diversity of racial heritage. Does focusing on diversity of racial heritage optimize diversity of perspective?
So apps developed in China or Japan or Nigeria will be at a disadvantage because they lack design diversity? Or will thru do just fine if they all went to different schools of design?
Nobody is "neutral". It's simply impossible. Therefore, diversity.