The OP was traveling on an award ticket (= "NO FF CREDIT" on the boarding pass). Evidently the OP was "bumped" (didn't clarify if it was simly a rebook due to IROPs, VDB or IDB). Sometimes when they rebook the ininerary, it will show in a revenue class (typically Y) and you will get credit for it. I've seen it happen.

To me, it appears that DL closed a loophole in the rebooking process, not "devalued a bump". There are other threads noting the same thing is happening for SDC.