To actually accomplish something like this purports to be (the linked tool only searches for similar images and doesn't tell you anything about how information ended up inside the model), you could try removing individual images or sets of images from the same artist from the training dataset to see what outputs the resulting model would lose the ability to create. It would be expensive to do that for more than a few images, but given how helpful it would be for the debate about copyright and AI, I think it would be great if some researchers could try it.