So I have mine, DL operated SEA --> MSP --> AMS and then KL AMS --> ATH. And I can't get that last leg upgraded even when Expert Flyer finds the Z. So I dunno. The DM line and Twitter seem to agree on this. They both claimed to have searched the KL flight number. The MSP --> AMS is already confirmed in Delta One. So I dunno.

The posts above seem consistent with this notion that Expert Flyer can't be trusted on this topic. Or the DM people can't be. Or both.