Is this gross or am i overreacting

I found pictures on my significant other’s computer in which he had used undress AI filters to alter my female family member’s pictures from dresses and/or workout clothes to nude. This includes my mother, my sister and my cousins. I am grossed out because he said it’s not sexual but that he’s experimenting with AI. However, if this was so innocent, I dont understand why was it being done in secret in the middle of the night. And why not use strangers photos or his own photos.