In the requirements and guidelines for App Store Review (shown below) it does not say anything about a return mechanism. It does however say "you should make sure you have a restore mechanism for any restorable in-app purchases." What this means is explained here.
App Store In App Purchases guidelines:
3.1.1 In-App Purchase:
If you want to unlock features or functionality within your app, (by way of example: subscriptions, in-game currencies, game levels, access
to premium content, or unlocking a full version), you must use in-app
purchase. Apps may not use their own mechanisms to unlock content or
functionality, such as license keys, augmented reality markers, QR
codes, etc. Apps and their metadata may not include buttons, external
links, or other calls to action that direct customers to purchasing
mechanisms other than in-app purchase.
Apps may use in-app purchase currencies to enable customers to “tip” digital content providers in the app.
Any credits or in-game currencies purchased via in-app purchase may not expire, and you should make sure you have a restore mechanism
for any restorable in-app purchases.
Remember to assign the correct purchasability type or your app will be rejected.
Apps should not directly or indirectly enable gifting of in-app purchase content, features, or consumable items to others.
Apps distributed via the Mac App Store may host plug-ins or extensions that are enabled with mechanisms other than the App Store.
Apps offering “loot boxes” or other mechanisms that provide randomized
virtual items for purchase must disclose the odds of receiving each
type of item to customers prior to purchase.
Non-subscription apps may offer a free time-based trial period before presenting a full unlock option by setting up a Non-Consumable
IAP item at Price Tier 0 that follows the naming convention: “XX-day
Trial.” Prior to the start of the trial, your app must clearly
identify its duration, the content or services that will no longer be
accessible when the trial ends, and any downstream charges the user
would need to pay for full functionality. Learn more about managing
content access and the duration of the trial period using Receipts and
This line basically means
if you delete the app, move to a new phone, whatever, your purchases
will no longer be available on that device. Restore Purchases asks
iTunes what of the available in-app purchases you've paid for.
It does say "should" which you could imply to mean that it is not forced but highly suggested.