[lacker]

In Apple's API you can send an encrypted message and have the app decrypt it. But you can't send an encrypted blob of data and have the app decide whether that blob of data was a message to be shown to the user, or a different sort of data like a read receipt. So the server needs to be able to differentiate the types of data packets sent from user to user, in order to use Apple's notification API, which is less private.

[oneplane]

And that would be a problem if having 'is typing...' and 'was read' notifications had to be pushed realtime to an app that was in the background. What is the point of those notifications arriving in the app when the user isn't using it.

[freeone3000]

The sender of these notifications doesn't know that the user has closed the app. What this means is that the message send from the sender through the server now has to include whether this is a message or a non-message, which has to be a flag in plaintext.

[oneplane]

But why use background notifications for this type of data in the first place?