The upload date of this image on Gelbooru, and therefore probably also the original deleted Pixiv post, is the 23rd of June 2019, which puts this right after a period where artists were being harassed on Twitter for drawing Nessa the "wrong shade". The most notable examples that I can remember being najuco_(naju0517) with post #3542576 and merryweather with post #3537686.
In support of them, other artists made posts like this where she is white, among them being hews with post #3541553. See also the comments there for more discussions during that time.
