In other words, the chapters are not, in general, agents delegated to do business on behalf of the Foundation. Instead, they are independent organizations who do outreach and education in service of the projects and the larger Wikimedia movement.
Well put, that's pretty much the way I see it. I consider chapters as part of the Wikimedia movement, not part of the Wikimedia Foundation (which they clearly aren't, from a legal perspective). Both work to further the projects, but they do so separately (cooperating where appropriate, of course).