From the FAQ mentioned in the OP :
For the purpose for this website, “stealth” means when an application is launched, used and terminated properly, it does not leave behind any entries in the registry or filesystem. Certain exceptions are permitted. For example, registry entries that are created/updated by Windows for the application (eg. MRU entries for dialog boxes, DirectX entries for DirectX-based apps), or temp files created in the official “Temp” folders are not taken into consideration. Note: “Stealth” does not mean non-traceability! In fact, it is quite unlikely you can hide your activities on a Windows machine from a capable system administrator.