So I think, but I’m not sure, this is for group chats. Group chats are only encrypted to/from the server because the server broadcasts the message to each recipient. As the messages are unencrypted on the server, they can feed them to LLMs.

This is different to Signal. On Signal it’s your phone encrypting each copy of the message before sending to each recipient individually.

…the ruling stopped short of ordering the government to recover past messages that may already have been lost.

How would somebody be meant to comply with an order to recover a message that has been deleted? Or is that the point? Can’t comply and you’re in contempt of court.