I also don't think it's a fair policy - because very often it's not that people don't want to do a roundtrip upgrade, but more often it's because CX is holding up the seats and just releasing them in the last minute (often after the outbound flight happens if your trip is more than a few days long), even if the return flight isn't really that full. It's much better for us DM's, but I have seen many of my friends/family members who're GO/SL "wasting" a lot of miles this way although they do want roundtrip roundtrips all the time to start with...but almost always got confirmed 2 x one-ways instead.