>the diversity policy is about making sure top talent doesn't go elsewhere

From what I know that doesn't seem to be the case at all, it's about projecting a positive image of your company (The candidates skills are secondary) (Though in theory the standards should be identical)

The hiring practices should be based upon who would be the best candidate (Experience, technical skills, personality, Education)

When you simply focus on what objective skills you need as an employer, you should find "Diverse"/minority candidates in proportion to what percentage of top candidates they occupy.

This surely creates the most level playing field?

One of the chief points in this article was that "diversity" is often an excuse to hire/admit people who will bring in a lot of money, connections, and prestige but aren't necessarily the most meritorious candidate.

Malia Obama is Diverse. John Dorsey from the wrong side of Chicago is just an Urban Youth.

No one can define "top"