NSURLErrorDomain is not returned.

https://developer.apple.com/documentation/storekit/handling_errors?language=objc

The official document says:

In case of network error as a result of request, NSURLErrorDomain is returned.

However, when I tried it in airplane mode (non-communication), SKErrorDomain was returned.

Code Block 
restoreCompletedTransactions

The result is different from the document.

This is not intended.

Does anyone have a similar problem?