To clarify, I'm not the creator.

Sizigi Studios uses a dataset I put together (https://www.gwern.net/Danbooru2018) as their primary training corpus, AFAIK, and they were partially inspired by my application of GANs to anime art (as demonstrated on https://www.thiswaifudoesnotexist.net/ and see https://www.gwern.net/Faces for much more detail about every aspect of it), but I have never been involved with them and don't know much about what they've done other than what you can read in OP. It tickles me pink to see people following up on my anime GANs, though, especially as a startup! The Great Work goes on.