The reason they didn't disclose it as being used in the creation of the game is probably because no AI was used in the ultimate development. It's an artist who uses AI to generate concepts and inspiration using AI in their artwork, even if everything in the end is hand crafted and doesn't resemble any of the generated images?

One thing we need to take into account going forward too is that AI will inevitably be used for things like texture maps and environmental generation. Things that have been randomly generated with algorithms. In a year it's going to be nearly impossible to say no game can have any AI used at all, unless you want the pool of potential to be incredibly small.