Yes, I am round tripping by sending a NEF to Photoshop via Catapult. I see no reason for the returning TIFF to be that different that what is viewed in Photoshop. And clearly,the histograms are displaying that difference.
What happens if you take Catapult out of the loop? Why are you using it? Can you confirm that the files you are comparing are based on the same RAW converter?
Did you try what I suggested? What was the result?
For trouble-shooting, I recommend ascertaining whether the undesired result is replicated in the simplest workflow, and, if it is not, add things in until you do replicate it.