The truck and 1500 platform has its limitations like any 1/2 ton or actually any truck on some level for that matter. It's quiet smooth fuel efficient and tows 1/2 ton appropriate loads extremely well. 340,000 miles on mine towing Airstreams other TTs & boats. The jeeps have a much smaller oil pan, engine bay, and taller gearing so they are more heat challenged when towing heavier TTs on the grades & in the heat.
I was on that thread on Airforums. He is not very mechanically savvy. Loved his Jeep the motor & economy but didn't understand that any vehicle can have the catalytic converter plug & fail. Funny he switched to a Ram1500 gasser had he picked it with the ED especially with the lower gear set he would likely be happy as a clam.
For OP I agree that seems stupid on Rams part to not allow it on build & price. I'll bet you can have a dealer price and build one for you. And you could still take that to other dealers for price comparisons. I would say anyone who wants a new ED should order a 17 quick before ordering 17s end. My BIL a long time Ram top salesperson has said it doesn't sound like we will be able to get 2018 EDs for quite a while and maybe not until MY 19s. I believe having to do with certifications.