Setting the Hidden attribute does not lead to non-functionality! I am only saying it is a Windows setting, Classic Shell will not touch Windows settings as there can be *POTENTIAL* problems in the future *if* Microsoft changes their OS as they like and people will blame Classic Shell.
This is not a bug or issue in Classic Shell!
Windows 8/8.1 ships with the empty Maintenance folder and the entire Start Menu folder structure is still created and maintained by Windows. There is nothing to fix in Classic Shell.
Microsoft can omit the empty 'Maintenance' folder in the next release of Windows. That is the only fix.