or are these the ones that have been tested?
Those are the ones that have been tested and
found to work by someone who was willing to take the time to write descriptive information and (usually) sample code that was considered "good enough" to make the cut among the folks editing that part of the site.
You'll find hundreds of different chips and sensors that people have tried out and only documented on a blog, in a youtube video, or in a quick posting to one of the forums. Or not documented at all.
As MikMo said, if in doubt about part "xxxx", try doing a google search for "arduino xxxx" and/or a forum search for "xxxx": you'll often find info that hasn't made it onto the "official" interfacing page. And, if all else fails, ask here.