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.