Is the <article> tag an appropriate wrapper for site documents, such as "Terms", "Cookie Policy" and "Privacy"? Or should it be reserved for proper articles, such as blogs posts?
<article> tagAccording to the W3 spec:
The article element represents a complete, or self-contained, composition in a document, page, application, or site and that is, in principle, independently distributable or reusable, e.g. in syndication.
It then goes on to list some example use-cases for the <article> tag:
This could be a forum post, a magazine or newspaper article, a blog entry, a user-submitted comment, an interactive widget or gadget, or any other independent item of content.
All that being said, I don't think the tag is really appropriate for wrapping your "terms of service" / "privacy" statements. While those could loosley fit under "any other independent item of content", I don't really think those items conform to the semantics of "a composition that is independently distributable."
Those types of things are very specific to your site, so I would say they don't fit the purpose of the article tag.
Here's a really good blog post on the HTML 5 article tag that I read: The article element