Ele é gerenciado pelo CSRSS, que é csrss.exe
Alt+Tab ↹ works even if Windows Explorer is no longer running. On Windows NT-based systems, Alt+Tab ↹ is managed by CSRSS (Client/Server Runtime Subsystem). It works even when Ctrl+Alt+Del and Ctrl+⇧ Shift+Esc (Task Manager) (which are managed by Winlogon) do not.[4]
https://en.wikipedia.org/wiki/Alt-Tab#Windows-specific_issues_and_hacks
Note que você só precisa enviar Ctrl + Alt + Tab ao invés de Ctrl + ⇧ Shift + Alt + Separador ↹
Using Windows 7 the additional key combination Ctrl+Alt+Tab ↹ brings up the switcher dialog and it remains on screen after all the keys have been released. A user can move through the dialog in any direction using the arrow keys, or Tab ↹ through in a linear manner, wrapping at the end of the list back to the begnining. In this mode, the ↵ Enter key or a mouse click selects the desired window which gains the focus and the dialog is dismissed; Esc dismisses with no change of focus.