As a dark skinned mixed race woman who grew up being abused, ridiculed and demeand purely for the colour of my skin it feels (to me) like fetishisation and yes like appropriation when white women go to such lengths to pretent they are another race purely because it is 'cool'
Rather than 'cool', I suspect that for many women & media celebrities it is about 'sexy'. The 'fashion' for having a well developed big bottom goes with that too. That's long been the look in places such as Brazil.....but is now pretty main stream everywhere now. most of the emphasis on women's bodies, certainly in the west, was always on the breasts, but now the bottom is the thing. Women have butt implants etc - to achieve that high, rounded 'African' backside.
Pornography probably feeds into this...with the emphasis on anal sex...and the mythical & supposed hyper-sexuality of black women.
I can't get too excited about people appropriating certain looks or styles....it is just fashion.....this is the nature of fashion..it plays with 'collective' images, fantasies and stereotypes. And in a multi-cultural world is not surprising that different kinds of looks have appeal - for those interested in fashion. Same with popular music.
Getting too precious about that would be like women moaning about Boy George wearing make-up and dresses.
It is not the same as actually claiming to be black in most instances.