Apple creates and presents a receipt for each Subscription renewal. Thanks to the S2S connection to Purchasely servers we will already know about that renewal.

There are specific cases when a receipt is required [by who? Purchasely], when the In-App Purchase requires a validation outside the App before the Purchase is completed :

Then Apple presents the original receipt validated outside of the App on App Start. We need this to associate the In-App Purchase with the right user.