There are documented values for Windows Vista to 10. The first Insider build of Windows 11 was just released, and the documentation wasn't updated yet, but perhaps it can be found somewhere in the system.
After a bit of fiddling around, seems like the current answer (at least for build 22000.51) is that there's no GUID yet. I found the list of GUIDs in ntdll.dll under the symbol SbSupportedOsList, referenced by a function called SbGetContextDetailsByVersion. The list contains only the five GUIDs mentioned in the documentation.