I think this is easy to resolve. With Netflix, the terms are that you pay a fixed amount and you get one month's access to stream whatever they choose to offer

I think this is easy to resolve. With Netflix, the terms are that you pay a fixed amount and you get one month's access to stream whatever they choose to offer at the time, repeat. If Netflix terminates your account, well, you lose out on less than a month of access, so they should refund one month. It's very different if (a) you pay per individual item, (b) there's an explicit or implied agreement that you have access to that item indefinitely. Then if your account is terminated, you should be refunded the value of having access indefinitely, which is the original purchase price. Now maybe you're saying Apple can go to a subscription service where it rents "access" to the library, but those are very different terms.