...What am I doing wrong
Nothing I guess, apart from switching to Adobe Camera Raw (ACR)...
- Most cameras create and embed a couple of preview images in their raw file.
- Photo Mechanic (PM) shows those preview images.
- Capture NX2 (NX2) replaces embedded preview images in the .NEF with the edited variant
- PM shows embedded previews made by NX2
- ACR does not change the NEF, not even embedded previews. Nor does Adobe Lightroom (LR) or Nikon's Capture NX-D
- PM still shows the embedded previews, meaning the original previews from the camera
- ACR and LR can update previews in DNG-files.