It is from Koikatsu. Linderball is a good egg and I believe him when he says he did not do anything untoward with the Sena model he made in the porn game, its just a convenient modeling tool for him to use. I view it kind of similarly to AI art generation tools - most of the anime ones afaik are trained on hentai content both because there's so much of it I guess and because a lot of people use the anime AI art for making hentai specific to their fetishes/preferences - and yet its used in FlaVR a crapton for just normal relatively seiso stuff. That said, I'd never heard of koikatsu until he mentioned it, so idk anything about it beyond what he's said and the content he's produced. They say the internet is for porn, but porn is now being gutted and having something useful stolen from it.