Little bit of everything. No cores. low sales, expensive, 2 piece rear main rope seals. got to the point where our core suppliers could only find RB blocks in motor homes, and they went out and bought larger crushers to crush Winnebago's. On top of the face we're not a rebuilder anymore. everything we do is brand new EXCEPT the 360 block we use on the 408's. And believe me, I make special considerations for those because I'm very partial :)
Also from a functionality standpoint, one of our Gen III's cost less, and does more, than an RB.
You're basically spot on, just giving some more insight.