The cursors were created for software released under the GPL license -> [link]
If you want the original cursors for X11 Mouse you can get 'em here -> [link]
Ported to CursorXP by
Ported to Windows Cursor using CursorXP base by me
Instructions: unzip, right click on obsidian.inf and install
Hope you like it
20090612: Updated, now small version included
PS: I just checked apparently they're not there in build 1809 but I can swear they were in previous builds.
It sounds like... a joke? Only possibility I could think of, is that Win10 is a custom build and the creator embed those cursors files right into the ISO and whoever get their build also get the cursors at default. But nearly impossible to have a chance that Microsoft actually set that cursor by default for enterprise edition.