The allegation is that the model was trained on a copy of the original work that was improperly obtained. The fact that it can produce a summary is being offere

The allegation is that the model was trained on a copy of the original work that was improperly obtained. The fact that it can produce a summary is being offered as evidence of that claim. You can't be sued for making a reference or whistling a song, nor you could have been sued for being in possession of a pirated copy, only making a pirated copy. Copyright law has many warts, but it's not some Kafkaesque mind prison.