Remember, the human that wrote a summary had to legally obtain a copy of the source material first too. It should be no different when training an AI model. There's a whole new can of worms here, though, since the summary was written by another person and that person holds the copyright to that summary (unless there is a substantial amount of the original material, of course). But an AI model is not "creating" a new, copyrightable work. It has to be trained on the entire source material and algorithmically creates a summary directly from that. Because there's nothing 'new' being created, I can see why it could be claimed that a summary from an AI model should be considered a derivative work. But honestly, it's starting to border on the question of whether or not what AI models can do is considered 'creative thinking'. Shit's getting wild.