> Does it mean that shreds retain original copyright even if the content can't be restored?

Yup, it absolutely does. In fact, that's why you are still violating copyright law by using bittorrent even though each of the users is only giving out a small slice or shred of the original content.

The US has a granted defense in the case of something like shredding called "Fair Use" but that doesn't mean or imply that a copyright is void simply because of a fair use claim.

> And the specifics of autoregressive pretraining is that it is lossy compression.

That doesn't matter. Why would it? If I take a FLAC recording and change it to an MP3. The fact that it was a lossy transform doesn't suddenly give me the legal right to distribute the MP3.

> Good luck finding which copyrighted materials have made it into the final weights.

That's what the NYT v. OpenAI lawsuit is all about. And for earlier models they could, in fact, pull out full NYT articles which proved they made it into the final weights.

Further, the NYT is currently in discovery which means OpenAI must open up to the NYT what goes into their weights. A move that, if OpenAI loses, other litigants can also use because there's a real good shot that OpenAI also included their works in the dataset.