I'd assume the precedent would be about sharing encoder data, which would be covered in bittorrent cases.

"Training a neural network" is an implementation detail. These companies accessed millions of copyrighted works, encoded them such that the copyright was unenforcable, then sell the output of that transformation.

Not being able to reproduce the inputs (each image is contributing single bytes to the neural network) is relevant. Torrent files are a means to exactly reproduce their inputs. Diffusion models are trained to not reproduce their inputs, nor do they have the means to.