Originally Posted by rucksack

I don't think that's what this is.

Delta underwent a fare realignment with KL and AF a number of years ago so that fare classes were consistent across the airlines. It seems like KL has gone a bit rogue with their use of the 'O' booking classes here and Delta's published earning chart simply doesn't yet reflect this change. If I had to guess, the fare realignment covered all flights as a matter of convenience, but technically only covered codeshare flights (which AMS-CUR is not), giving KL latitude to make this change.