Availability guarantees of ntdll.dll functions in the metadata

[Fulgen301]

The metadata contains some ntdll functions, e.g. NtCreateKey. According to a search in the repository issues, those are all documented functions or Nt* - variants of functions where the Zw variants were documented. However, like NtCreateKey, not all of them are actually documented as part of ntdll, but instead as a kernel-mode function in ntoskrnl.exe (I am aware that ntdll contains the user-mode syscall equivalents, but the documentation makes no mention of that).

As this is an official crate by MS, can I rely on those functions being present in future versions and updates of Windows?