Backyard-Birds Sample Code issue

In Apple official example code "Backyard Birds", is this code wrong? For I've tested this code many times but this part has never been executed!

.onInAppPurchaseCompletion { _, purchaseResult in
            guard case .success(let verificationResult) = purchaseResult,
                  case .success(_) = verificationResult else {
                return
            }
            showingSubscriptionStore = false
}

This modifier decorate code as below

.sheet(isPresented: $showingSubscriptionStore) {
     SubscriptionStoreView(groupID: groupID)
}

Is it because the modifier onInAppPurchaseCompletion only works with ProductView ?

It's AppleWatch part. But I can't purchase in Apple Watch app because there is no code to finish the transaction

By default, StoreKit Testing in Xcode is disabled. After enabling this by selecting the StoreKit Configuration file for the scheme, you will then be able to complete purchases in both iOS and watchOS for this Backyard Birds project. For information see StoreKit Testing in Xcode. If you continue to have issues, please provide what errors you are seeing and how to reproduce them.

Backyard-Birds Sample Code issue
 
 
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