Variation in (Black) Hair by Mattel

Short Black Hair - Avon Representative, Uptown Chic, and Princess of South Africa Barbies
I had thought that the Uptown Chic Barbie and the Princess of South Africa Barbie had flocked hair. Opening the box, I see that the straight hair is cut very short for Uptown Chic Barbie and tightly curled and short for the Avon Representative and the Princess of South Africa Barbies.

Flavas Denim and Diamonds Kiyoni Brown and Generation Girl Nichelle, Long Stiff Hair

People concerned with ethnic authenticity allow that Black hair can be long, but they would find that the texture is usually coarser, curlier, and/or "heavier" than "White hair" or "Asian hair." Black hair is usually NOT "flippy, tossable." See Kiyoni Brown and Nichelle in the photo above. With the Denim and Diamonds version of Kiyoni Brown, Mattel captured this heavier, coarser hair texture. Kiyoni's hair looks like it could have been straightened with a hot comb. Nichelle, in contrast, has slightly relaxed, corkscrew curls similar to but mercifully NOT wet and greasy like the Jheri curl hairstyle worn during the 1980s by Rick James and Michael Jackson.
Here is Kiyoni alone for a closer look at her hair:
Flavas Denim and Diamonds Kiyoni Brown

Use of some of these hair styles rather than the default straight or wavy hairstyles used for the S.i.S. dolls might have satisfied the "authentic" requirement.