StoreKit resending all purchased events if the user tries to buy the same active subscription [sandbox]

I'm testing an auto renew subscription in the sandbox, one scenario I am testing is to make sure I can handle if I accidentally show the user the purchase button for a subscription they already purchased.

In the sandbox when the user clicks buy iOS pops up an alert saying the user already has the subscription, which is good, and doesn't charge again but then I receive one event for every subscription renewal the user has ever had, basically all their previous purchase history via:

func paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction])

Is this expected behaviour in production, or just a sandbox quirk?

Thanks.