What does the SuperHidden Registry value control?

There is a value called SuperHidden under this Registry key on some versions of Windows:

HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced

It's reminiscent of Hidden (which controls whether the user sees hidden files in Explorer listings) and ShowSuperHidden (which controls whether the user sees system files in those listings). One might wonder what SuperHidden controls.

And the answer is... nothing! Using Process Monitor, I observed I/O to it and found that it only gets written when the View tab of Folder Options is shown. It's never read, even when Explorer is starting, so it can't control anything. So why is it there?

Investigating the stack provided by Process Monitor led me to shell32.dll, which issues a write to that value in CachedShellState::SaveAdvancedSettings. The corresponding function CachedShellState::_GetAdvancedSettings, however, issues a read from ShowSuperHidden, the value that actually does something. I also noticed that on Windows 10, the inert SuperHidden doesn't exist, and sure enough the Windows 10 version of shell32.dll writes to ShowSuperHidden.

Therefore, I strongly suspect that the existence of SuperHidden was a typo that was later corrected.

Based on my Super User answer.