FltSetSecurityObject returns STATUS_NOT_IMPLEMENTED

NTFSD Folk:

I’m getting 0xC0000002 (STATUS_NOT_IMPLEMENTED) from FltSetSecurityObject.
This is on XP SP2, but I think it’s consistent on other platforms.

ZwSetSecurityObject works fine, even on Windows 2000 (in spite of the fact
that the documentation says “XP and higher” ).

Is this a known problem in FltSetSecurityObject? Any reason not to use
ZwSetSecurityObject regardless of the documentation?

Ken