If you check the non-stop fares out of ATL, there isn't really any fare bump pre and post D1 designation. What's happening here is that for fares prior to the D1 change, there are single, through F fares available from many origins. Post D1 designation, you are only getting broken fare pricing with an F fare on the segment to/from ATL/MSP combined with a D1 fare on the ATL/MSP to HNL segment. The broken fare construction can be seen when you click on the fare rules. I suspect they are still working on the fares on these and at some point there will be single through D1 fares so that you don't get stuck two separate fares (an F and a D1) when connecting to the HNL flights.