I don't think you're missing anything and I think many Reserve cardholders will rethink how they use the car. Now that I've seen how my MQD earning is working, and will my MQM conversion, I will likely stop using my DL Reserve after I hit DM in the next month or so. Everything will then go to my AMEX Plat. This will likely be a reduction in spending on the DL Reserve from about 100k annually, to 50-75k. It will depend from year to year based on my actual flying and if I want to maintain DM. I've been PM for 15+ years and always made sure I didn't make DM. Now that there's no rollover, I'll just go for PM or DM based on my flying/spend.

One note: I don't use either CC for SkyClub access since I have an Executive Membership. (I travel with staff often, and it's the best way to get them in)