It's very simple. Nolan wants to win another Oscar, and he can't do it without adhering to new AMPAS rules about minority representation.

I don't think this brouhaha will have any effect on commercial prospects on the film - either positive or negative. What is more likely is that Nolan has inoculated himself from the critics who would have ripped his film to shreds, but now must praise him to high haven in order not to be mistaken for bigots.