Honestly, it's pretty obvious it's not AI art. But I get why people would say it: it's literally just the shading. That same style of desaturated shading is the kind of thing people usually train their half-baked AI on (because it looks good!). But you can see even in the preview images how that shading style is used pretty much exclusively on good ol' T&A, where-as an AI would cover every facet of every surface with desaturated highlight and lowlight gradients. Heck, there's even some loose stippling used here, which you never see with AI art because it would just smooth it out as a visual artifact.
Personally, I've never been a fan of the "I make pin-ups on Patreon" art style this gradient-heavy shading was associated with pre-AI deluge, but I really like the overall posing and the foundation under it (Looking at the Cornelia Blowjob preview image in particular).
I'm excited to try the game itself, since it's veiled in mystery due to everyone just talking about the art style (myself included now).