I have an app in store which has in app subscription, while checking for renewal it is not providing me exact end date of subscription based on which I have to lock / unlock certain features. It never fetch right date to verify, this is seriously a little thing which seems to be too complicated.
Tough to determine what is being used here but if using StoreKit2 then currentEntitlements handles much of this for you.
https://developer.apple.com/documentation/storekit/transaction/3851204-currententitlements
Keep in mind the expirationDate is part of the transaction: https://developer.apple.com/documentation/storekit/transaction/transaction_properties