The NVAPI bits only bridge a gap in OS support. 95% of the stuff described is standard D3D, but additional data is needed in identifying displays and setting up metadata. Theses APIs serve that purpose, until the OS catches up (or allow things to work on older OSes). Chas Boyd from MS actually gave a talk at GDC on future HDR support on the platform. What was described in the talk was compatible with what is described there. (Next post in the blog series actually has a link to the YouTube video)