Ok, can you (1) switch to SM5 in the Editor, by toggling the Preview Rendering Level like in the video below and then (2) check the different LODs in the Static Mesh Editor using the LOD dropdown (as below). Are any of those LODs exactly the mesh you see in the game (ie same pointy top?). Note that you will only see the different LODs properly if you are in SM5.
Also, on SM6, could you put this skull in the center of the viewport and take a screenshot of the Nanite Overview visualization mode (in the level)?
Based on your screenshot above, the auto-generated LOD0 mesh used when Nanite is not being used has the same tri count as the Nanite mesh. So, you would not see a difference in LOD0 in the Editor regardless of whether or not Nanite is enabled.
What I am trying to figure out via these questions is if you are seeing one of the existing LODs in the game, or if you are seeing Nanite. Unfortunately there is no real way to tell this for certain in-game, we have to infer it from what you see in the Editor.
