The third injection event and probably modified valve timing is equivalent to in cylinder egr (a poor man's approach). We get the filthy oil without the benefits of a VGT. The result is that DC saved a buck. Cummins is losing its reputation for efficiency, and we are getting ripped off at the pump.
If you compare Cummuns off road and on road emission approaches you will find we got the cheaper off road fix (less efficient -- but cheaper). Check also John Deere. They have two approaches too. They use the approach Cummins used in the 600-610 only for those who want to minimize installed cost and do not mind significant losses of performance and efficiency.
As proof, Cummins advertises that the egr isbe is 2% more efficient than the old 24v engines. However, they do not even bring up the subject of efficiency for the Dodge variants of the isb engine (e. g. 600-610).