It’s both. Governments have started subpoenaing the push notification servers for data, instead of targeting individual devices. That little pop-in that says who the message was from, and maybe a little bit of the body of the text? Yeah, the push notification server handled that, and the government has access to that server. So any notification you see on your screen, you can be pretty positive that the government has also seen.

But this is about the notification data being stored in a part of the phone that isn’t encrypted. Signal is (or at least claims to be) E2E encrypted, so it shouldn’t be possible for a warrant to get access to the messages in the app. But since the phone is storing those notifications in a separate area (which isn’t encrypted), the warrant was able to read them.

The point is that there are two different attack vectors, and you should harden your device against both.