I asked myself, too, what an encrypted disk shall help if you hit certain situations.
Pro:
- somebody - without your knowledge - wants to copy your disk
- dito wants to install something on your disk
Con: - somebody wants to force you to show the content of your disk
The only solution in the latter case is to open the box for the intruder. If you’d be able to open a secondary encrypted disk/partition without him noticing, everything would be fine. If you’d have to decrypt your primary, everything’s lost.