Chapter 17 tries to explain the different between stopping+restarting and rebooting. It might be clearer if you can add a note that stopped instances loose their association with the virtual hardware, and the association is kept intact while rebooting.
Updated the documentation based on Niels suggestion and the latest documentation is available at: http://documentation-devel.engineering.redhat.com/docs/en-US/Red_Hat_Storage/2.0/html/Administration_Guide/chap-User_Guide-aws_stop_start.html