The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the FSRTL_X.H header at


and draws from it the following type definition:

Line Number Type Remarks
158 struct _FSRTL_ADVANCED_FCB_HEADER line 16411 in NTIFS.H

The header FSRTL_X.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).