The new approach might be useful as GUC protection, as mentioned by BenA. If they're not going to allow any mileage upgrades DoD they ought to manage mileage upgrade inventory (and GUC) more actively T-72 to T-24.
We're not going to see any data on how many J seats KL sold from AMS vs. other markets ('protecting the premium cabin'), nor how many J seats went to nonrevs. But Delta knows. KL can accuse Delta of just throwing away $.