Does the SKPaymentTransactionObserver get events not caused by my API calls?

That is, do events come in from Apple that originate with them, not in response to my calling SwiftyStoreKit?

I call SwiftyStoreKit.completeTransactions() at launch. I understand this registers the observer, which SSK manages for me. All subsequent interaction with the (hidden) observer come in completion handlers, which handle callbacks from specific requests I make. (E.g. retrieveProductsInfo, purchaseProduct, etc.)

What happens if an event is posted to the observer that is not in response to a specific call I make? How would my app be notified? Does this even happen?