Yes, my simplification was a little misleading, and even this response will be too. Thank the lawyers for generations of building their own job security into the statutes.
The key is that, really for the first time, there is a differentiation between access and reproduction. They are saying that fair use can allow you to circumvent a system the prevents reproduction, but it does not all you to access (decrypted) the information. So, you are probably protected by fair use when copying a DVD as a backup. But you are not OK in decrypting the contents of the DVD for you to access the actual data.
So, when they say that they are allowing circumvention for copying because of fair use, it is a red herring. Fair use covers a whole lot more than just making a bit-perfect duplicate - more often it includes using some transformative version like an excerpt or transcoding to a new format for research, commentary and educational purposes, among many others. But if you can't decrypt it to get at the pieces you need to work with because of the access controls, fair use is effectively nulled. And of course, don't forget that while circumvention may be legal in certain cases, tools that are designed to enable either kind of circumventation are effectively illegal to create or sell. Which makes it real hard to legally exercise your right of fair use.