The idea is "one application per virtual machine", and to leave multi-tasking to the browser. Right now the only application we have is Warcraft.

The fact that you can interact with Windows outside the context of the intended application is a side-effect of Windows 8 Assigned Access only working for "Windows Apps" (ie- not "legacy" applications). Otherwise we would have gone for this type of "kiosk" experience which attempts to hide the underlying desktop environment / os.