My own theory about why the problems are centered around Dodge / Cummins right now is simply the quantity of EGR going back through the engine.
From looking at my monitor for EGR valve position mine is 94.9% open almost all of the time from idle to empty highway cruising with is the majority of what I do. EGR flows seem to be less as the load goes up, on hills and running heavy there might be as little as 7% to 40% but every possible second that it can it is 94.9% open.
Ford and Chevy are both running EGR on their light / medium duty diesel engines but I believe the quantities are less - just from lurking around the various message boards related to those two products I've noticed that their DPF DeSoot cycles (regens) occur at least half as much as mine do. I also have data (not at liberty to disclose the source) that suggests that with the EGR capped off on the 6.7 and the DPF in the system the soot delta pressure increase (a basic measurement of DPF backpressure or how clogged it is) is over time is greatly reduced suggesting a huge soot load increase due to the EGR, however EGR reduction can have a seriously negative impact on the Nox absorber that our trucks have been blessed with.
It is possible that many of those million customer equivalent miles were high load miles on a load cell or something to simulate towing conditions and not light load miles like many of us do, or the EGR mapping was different during the testing, or they only meant that the 6.7 itself was tested for that long and then turned over to Dodge who programmed the whole mess - who knows how much factual data is behind what the propaganda machine at Cummins / Dodge spews out.
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07.5, 6.7, Auto, QC, 4x4, Lots of gauges - ISSPRO (Pyro, Boost, Trans Temp) PriCol Optix (Fuel Pressure Lift/Rail) AutoMeter (Oil Pressure) - Dynatrac Free-Spin Hub Conversion Kit - RETRAX bed cover - homebrew shaved bluetec badge - plugged up EGR - Baldwin BF1212 water separator and CAT 1R0750 fuel filter - MSD Dashhawk - Baldwin B164 Bypass Filter - BD SBS