I've just read that with VeraCrypt it is impossible to determine whether there are hidden files or not. Sure, the rest could be free disk space. But couldn't a nasty coercing person that is scornful and envious about not being able to access your files force you to not only give the password to the non-secret container, but also force you to write so much stuff into it that the stuff from the secret container will sure be overwritten, so you will lose all your files?
... and of course the other thing the malicious coercing person could do, is say "fine, I don't believe there's no other hidden files in this container, so, copy everything out of the container and delete the container."
This would completely defeat the purpose of the hidden stuff in the container. If that stuff is nowhere else, you could lose everything! Just imagine! Thanks.