Call it what you will, but it's a sensible solution.
In case you don't quite get the backstory, AMC created season 5 part 1 and sold it through Apple under the name 'Season 5'. Then they released season 5 part 2, and started selling that independently. A bunch of people who bought the item labelled 'Season 5', said, "Whoa, I already bought season 5. Why do I have to buy the second half of season 5 when I already bought the whole thing?"
So essentially Apple is providing enough in-store credit so that, if you bought the first half, you can now get the second half for free. Giving an actual refund is problematic. Beyond the fact that businesses would rather provide store credit than a refund, it's a pain to deal with all the different possible cases. You have people who bought both the first half of the season and the second half, and you could give them a refund. But then what about people who have bought the first half of the season, but hadn't bought the second half. It doesn't really make sense to provide *them* with a refund, because they thought they already got the first half. If they didn't buy the second half of the season, then you're just giving them the first half for free. What would make sense is to buy them the second half of the season, and attach it to their account.
But then, what if someone got fed up and bough the second half on Amazon or some other service? What if they decided they don't like the show, and they don't want the second half? What if there's some other scenario that I'm not thinking of?
So the best thing to do is to give store credit. If they want to buy the second half, then they can buy it with the credit. If they have already bought it, or if they don't want to buy the second half for some reason, they get an equivalent credit to do with as they please, but they aren't permitted a refund on the purchase of the first half of the series.