The bigger problem is grep. We're told that grep prints lines matching a pattern, great. But then the explanation of the arguments makes it sound, to the uninitiated, like I'm giving "foo" as the filename, because the site doesn't include the actual grep syntax.

It doesn't really explain what the command line is doing. It does seem to do a decent job of telling someone who's already fluent in shell usage the specific meaning of all options given. That's actually pretty important these days where any given GNU util will have flags for every single letter of the alphabet in both upper and lower case.