Delivery of auto-renewing subscriptions for iOS

Question

I am finding that the renewal of an expired auto-renewing subscription is never being delivered while the application is active and running, but rather when the application is woken up from background or on launch.

In other words if you are using the app, and the subscription expires, it won't be delivered to the app (assuming it is auto-renewing and valid etc) while the user continues to use the app.

This behaviour does not seem to be documented by Apple, can anyone else with experience of this confirm or otherwise?

Obviously one can detect that the sub has expired and then offer the user the chance to check their subscription status and restoreCompletedTransactions which will pull in the new subscription - but I'm just wondering if we're doing something wrong, or if this behaviour is normal.

Thanks.