This option exists in the product at all only because it is retained for backward compatibility with images created with very older versions (Ghost will still read images created well over a decade ago). However, even in 1997 when the switch was introduced, the implementation was sorely lacking from a security standpoint - as it happens, prior to my main involvement with Binary Research I was tasked with looking at this to review its security, by being given a pre-release binary to see if I could "break" it, and my emphatic recommendation was that it not be released as it was.
Do not rely on this as a security feature; it is not. There is no direct support for this feature in the Ghost console system because this feature is not implemented to a suitable standard to provide effective security.