I think it is confusing – I would personally say it is a blogging tool. Even MT is a blogging tool and they haven’t evolved or matured into CMS’s as such, they can be made up to closely resemble a CMS. I think Denis-de-Bernady’s plugin does a decent job of it, but it’s not a CMS out of the box.
E107, PHPNuke, Mambo and the like are fully featured CMS software. BLOGCMS has tried to work as both a blog and CMS and it’s pretty poor as a migration between the two. MT, WP, and TXP are also blogging tools, that can be made to look like CMS but again they’re blogs out of the box.
The Majority of CMS tools come built in with about 101 features that allow you to immediately create a community or business portal. CMS can be used as a blog, but there is a distinction. There are quite a few articles on this that you might Google for.