i suspect part of the reason he brings in permission, is to support the "generative AI is plagiarism" narrative, which i think is largely bunk. but that doesn't mean it can't be used plagiarize. the "create image in style of XYZ" feature is a good example: if you do that, you are very explicitely basing the result on a specific persons work, and i think that calls for credit (obviously you shoudn't claim that they _made_ it, but that it's generated to be in their style, just be frickin honest…).