It is added protection. The courts can look the Bill of Rights in the face and ignore them as we have found out. It hems the government in even more.
If it is Unalienable it is incapable of being sold or transferred while if it is Inalienable it is not subject to being sold or transferred.
The status of whether or not something or someone is "subject" to something is changeable, the statement that it is not possible to do so is rock solid.