I have included various localized descriptions in iTunesConnect (English, French, Chinese) for an in-app product. I am displaying the localizedTitle and localizedDescription pr
After further testing I have confirmed that @claireware was in fact correct in his answer.
The tester is not able to manually change or set the store for testing (Apple docs state not to login with test user (Settings=>Store=>Signin)). However if you make a test purchase and enter the test users credentials at the prompt the device will warn you that it is changing to the test user country's iTunes store. After you make a test purchase the test user will be logged in and your subsequesnt SKProductRequest will return information localized for that store.
In summary for localization testing I followed these steps:
I believe the localization that the store returns for the product description is based on the assigned iTunes store of the test user you are using. The device's language setting only pertains to the resources loaded locally.