Description
When reading notifications on the lock screen or notification centre, VoiceOver will often speak the term "Collapsed stack" on the notifications.
This implies that there are more notifications hidden behind the currently focused one being read, and this is sometimes the case. If so, selecting will will reveal more notifications.
On some occasions however, it is an individual notification.
Selecting it in this case will open the app.
So the user does not know what to expect, or what action will be taken if they select the notification.