I found out that having multiple apps installed on your device that share the same initial bundle identifier "com.yourorganization" can lead to this issue. Either removing all other apps from your organization or changing the bundle identifier entirely resolved the issue for me.
Prior to this adjustment, when testing StoreKit locally using Xcode, StoreKit purchases were not correctly reset upon app uninstall/reinstall, resulting in some purchases persisting even after the app was uninstalled.