I will add that the PUREE specification does support subvolumes: different passwords may unlock different regions of the disk. Yet, while the spec is quite simple, this feature isn't implemented yet, nor is the ability for a PUREE disk to be bootable.
My hope is that, despite PUREE currently lacking these features in version 1.0.0, anyone who has been discouraged by the learning curve and installation overhead of the alternatives will find use in PUREE, given its simplicity, clearly strong security properties, and user-friendly interface.
However you should be aware that this property is not widely considered a "good thing" because if you are in a situation where an attacker is willing to physically harm you, then they may not be convinced that you've given them all of the keys (even if you have). The same problem exists for cryptosystems that self-destruct -- how do you convince the attacker that you weren't the cause of the data being destroyed?
You would think it would be the obvious action, but history has taught us people can go a long way in trying to convince others they are right, when they are not.
Hat tip
The reason why that's not the focus of TrueCrypt/VeraCrypt is because they also go significantly further. One problem with plausible deniability with this concept is that it's difficult and limiting to have to try to hide traces of access to an encrypted disk from a host OS that is stored on unencrypted media (and, obviously since it's the point of the whole project, even if it was encrypted, you could be compelled to decrypt it.)
TrueCrypt/VeraCrypt FDE supports hiding an encrypted, bootable partition within the free space of another encrypted, bootable partition, in such a way that it is not generally possible to tell that there is a hidden partition, but you can boot into either depending on what password you enter. (Of course, the bootloader that allows you to enter the password is not encrypted, so for bootable partitions there is evidence that some encrypted partition exists, but this is unavoidable.)