I haven’t seen the exception but there could be ways that it’s crafted that wouldn’t necessarily make it pointless. It would allow private copying but still prevent the uses that are technically restricted to the author of the work, meaning distribution or public performance of the work. That would still be considered infringement. You could break the DRM and make a private copy but you can’t break the DRM and make 160 copies and sell it. It doesn’t render the provision pointless, it just makes clear that there are certain limited uses that you’ll be able to do.