A google for "windows inode" and following some of the links there came up with

• A concept similiar to inode exists also for NTFS -> https://answers.yahoo.com/question/index?qid=20090805195409AAJDwM3
• Windows stat does not handle it (gives always inode 0), but there is a FileID usable for this purpose (via http://stackoverflow.com/questions/10511151/do-directories-in-windows-have-an-inode-number)

Using that FileID in place of an inode number needs ino_t being able to contain 128-bit-values, which probably was too big for the "older" unxutils.

Update: I don't know if GnuWin32 actually uses this, it's just a guess...