Why wouldn't it be true? That's the purpose of the training, no? To generalize the model so that it can produce images it has never seen before. That includes

Why wouldn't it be true? That's the purpose of the training, no? To generalize the model so that it can produce images it has never seen before. That includes images in styles it has never seen before. Whether or not models have generalized to that point is a different question, but if they do, (and let's be honest, alot of artistic styles aren't that unique or different) the only thing that would be different is that the model cannot conjure up the style by providing the artists name in the input, instead one would have to describe the style in other ways.