I heard that these 6.7 has a ceramic coating in there turbos and that is why they took issues with the CK-4 oils. Yet, there were CJ-4 oils that were lower in there zinc or ZDDP that Ford never made an issue of.
The big issues with the turbo in the pickups was the design.
They were concerned about valve train wear, specifically the rocker arms, with CK4 oils, not the turbos. The turbo in the pickups is different from the cab and chassis trucks.
The valve train is unique to the 6.7. 32 valves, 32 rocker arms, 32 pushrods, and a unique hydraulic lifter that utilizes 2 small hydraulic tappets in an oversize roller assembly.