When I adjust the altitude on the hdr map it actually rotates the map rather than adjusting the height. When I render using vray or brazil it adjusts correctly and in the render viewport also is fine, but for some reason not in Neon viewport.
The HDR texture altitude adjustment is working here for me. Can you check your version of Neon and Rhino 5 is the most current. If that doesn't fix it for you, please send over a 3dm file with the HDR embedded in it (Options>Doc Props>Rendering) before saving. You can email this to me at tech@mcneel.com, just make it attention BrianJ please.
Please also check out this forum for Neon... I believe it will become the default one shortly