Some subscription events trigger multiple notifications. For example, when a user upgrades their subscription to another SKU three notifications are sent: CANCEL, DID_CHANGE_RENEWAL_PREF and INTERACTIVE_RENEWAL.
The order of their arrival is obviously not guaranteed even if the order of sending is the same.
However, I wonder whether we can expect that unified_receipt will contain the same information in each of them? The docs do not mention this explicitly, but it is quite important for what we try to build.