I think everyone has gotten it wrong. I don't think Negisaray does AI generation at all. There are really good digital artists who don't use AI at all. I have a friend who does digital art and some of my friend's artworks do resemble Negisaray's techniques.
When I requested my commission, Negisaray gave me a PDF file on how they operate. They showed the "rough" or "non-detailed" art and then the "finished" product and just from my short review of that PDF file, I can confirm that Negisaray actually paints their work and doesn't use AI generated images. The "rough" or "non-detailed" version actually looks legit like a painted digital art where you can see the brush strokes and air brush splotches. AI can't do that. I've seen AI generated art and a lot of them don't look as realistic as Negisaray's artwork. A lot of them look very rubbery, for instance, look at this AI generated art.
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Looks pretty "real" however the difference between Negisaray's and this kind of AI generated art is that with Negisaray's you can actually tell the art was painted. With the AI generated photo above, it looks very rubbery and "too realistic".