This issue seems to apply only to simulators. iOS 14 beta 5 on a real device receives products as expected.
Simulator support for IAP has always been weak. Product requests do still work on iOS 13 simulators, but not on iOS 14 simulators in Xcode 12 beta 5. You'll need a beta installation on a real device to test IAPs properly.
Topic:
Developer Tools & Services
SubTopic:
Xcode
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