Media passthrough isn't the same as streaming from the HTPC. IF you look directly above the quote above.
For a HTPC, this means HDR support must be in the video, GPU, video interface (HDMI/DP) and ultimately your output device (typically a TV).
HDR10 is supported on HTPCs under Windows, macOS Catalina, Android and (usually) libreelec/coreelec operating systems. Linux is NOT supported.
So you if you have a HDR10+ source on your IntelNUC, or whatever, you can play that over HDMI 2.0 to a compatible TV without an issue.