It is clear cut because the Stable Diffusion AI you refer to was nevertheless trained on public data to get to that point were it could then be 'fine-tuned' wit

It is clear cut because the Stable Diffusion AI you refer to was nevertheless trained on public data to get to that point were it could then be 'fine-tuned' with your own art. Your own art is just a small addition to its much, much larger input/training set. The size of these public training sets are truly massive. If you start with a Stable Diffusion program from scratch with all weights initialized at random (or whatever weights its initialization algorithm requires) and you train it on only your own photograph(s), then you will almost certainly find that it's not effective at all. In that case though, the low-quality output would be 100% your own. The reason why generative AIs are so good is precisely because they have access to a large body of public data. Without the public data, they would not be good no matter how good the underlying software/algorithm is.