Neither of those says that anybody other than sender and recipient can access message contents. Just metadata, which is well understood (and from what I know, also true for Signal, correct me if I'm wrong).
The subpoena asks for "all correspondence with [these] users". I am not a lawyer, so I don't know if that gave enough wiggle room for Signal to not provide metadata, or if they don't store it in the first place.
Where does it say that? It says they could do that, not that they are doing it.
Although nothing indicates that Facebook currently collects user messages without manual intervention by the recipient, it's worth pointing out that there is no technical reason it could not do so. [...] An "end-to-end" encrypted messaging platform could choose to, for example, perform automated AI-based content scanning of all messages on a device, then forward automatically flagged messages to the platform's cloud for further action.