Interesting. So, the Labour Party was worried that all its candidates for leader were Oxbridge-educated people, whose only careers before entering politics were in political research/lobbying/media/PR, and hence they decided to spread the votes around to get Diane Abbott on the ballot. Because...well...she's Oxbridge-educated...and her careers before entering politics were in the media, PR, and for a lobby group.
Err...okaaay. So they didn't actually care about achieving any actual diversity. What they cared about was cosmetic diversity achieved by the brute fact of her being, not to put too fine a point on it, a woman.
(And no, before you ask, I don't think that skin-tone was the crucial factor, or even particularly important - Ed Balls had considered Yvette Cooper because she was a woman; Harman voted for Abbott because she was a woman. There is definitely cosmetic tokenism here, but it's gender-driven, not pigment-driven.)