Normal overhead valve service for a pre-2019 6.7 CTD was to check the clearances at 150,000 miles and adjust if needed. I’ve opened a lot of these engines up at that interval and don’t remember many that ever needed any adjustment at all.
The cam itself is different. As
@Brutal_HO said above, the cam is hollow and is supported across the block by more bearings than what was previously done. It also has a different lobe profile. The ramp rate on the lobe is more aggressive. This is actually one of the areas being questioned / investigated. There’s a chance that aggressive valve actuation is partly to blame for the rollers being damaged prematurely.