More often, the person is just a token hire who functions more to ensure legal deniability on the company's part for anything that might pop up related to a diversity issue.

I hope more companies hire diversity officers for the sake of thinking hard about how to ensure that policies and company behaviors aren't harmful.

But for me it's a "I'll believe it when I see it" sort of thing. The default belief has to be that it's just a token position for the sake of legal deniability, just as most of HR has evolved into.