Hidden system volume option disabled

[Anonymous]

I'm about to encryp my entire or in this case system volume. As the hidden volume option is the one I usually go with I wanted to use that option in this instance as well, however it's not available and I can't figure out why? I have read through the documentation on Veracrypt in general and hidden volumes in particular and can't find any reason why this shouldn't be available to me. Can anyone explain?

Thanks!