Can't create single-file .exe.
Even without Au.dll would create ScriptName.exe + ScriptName.dll. With old .NET 4.x could be single .exe file, but for .NET 6 need .exe and .dll.
Au.dll performs many auxiliary tasks, for example prints exception info when failed, allows to terminate more softly (remove tray icon etc), sets script class properties, workarounds for .NET/OS bugs, etc.
Even without Au.dll would create ScriptName.exe + ScriptName.dll. With old .NET 4.x could be single .exe file, but for .NET 6 need .exe and .dll.
Au.dll performs many auxiliary tasks, for example prints exception info when failed, allows to terminate more softly (remove tray icon etc), sets script class properties, workarounds for .NET/OS bugs, etc.