Thanks Steve for the comment. Agreed, it does not make sense to use the CC-SA 1.0 license - for the reasons you mention and also because it is out of date and lacks some of the requirements included in the 3.0 licenses (e.g. relating to DRM) - hence the "share similarly" approach suggested here.
Apparently, in Europe it is not legally allowable to release your work directly into the public domain. The only way for one's work to be in the PD is for its copyright to expire.
Do you know of any "no rights reserved" licenses? As far as I can see there is still a need for a license that would be more or less equivalent to PD.
This Libre License is also trying to make a stronger statement about consistency right down to the requirements for free data formats and free software for manipulating and sharing knowledge resources. It is more about a shared set of values around inclusivity: see Declaration on libre knowledge.