That documentation completely misses the point :( There's no list of what actions to use in the factory, or that a login action has setPassword method (as you're using the magic method __set(), those things aren't listed by phpDocumentor). It's that kind of things what I'd want to view (or an explanation on how to map the api documentation to dementia).
Like most generated documentation, the audience is more developers than end users (I hope to do a better write-up soon for end users, including what the core goals of the framework are, but I'm aware that my progress is slow at the moment). All of the methods to use on an Action or Query instance *are* listed, though; you can get variables, set variables, and execute, and that's it.
The variables you can get or set depend on what action or query is specified, but there is not a separate framework class for each action or query. The variables are by necessity defined in the API documentation (e.g. http://www.mediawiki.org/wiki/API:Allpages) and not the framework documentation; while I could write up examples using the framework for each type of action and query, I couldn't possibly cover the sheer breadth of options that are available in the API.
The point at the moment is that the framework automagically handles all prefixing of parameters, including generators' parameters, so the end user's code is more readable; it also continues queries automatically and selects an appropriate backend for actions and queries (which is its primary purpose).
Does that make more sense? -Madman