This bill actually does very little. The DMCA is written very broadly, and has been commonly interpreted as to prohibit cell phone unlocking. Because Congress, in the 90s, when they enacted the stupid thing, was aware that the DMCA could go too far, but didn't want to be cautious or have to keep reexamining the law itself, they gave authority to the Library of Congress to add exceptions to it in specific cases. The process for these exceptions is that every three years, anyone who wants an exception has to plead their case. If found worthy, they get an exception. But the exception only lasts until the next rule making session, three years hence. Then it has to be reargued from scratch or lost.
Two rule making sessions ago, the Library of Congress found that cellphone unlocking was worthy of an exception. But in the most recent rule making session, they did not find it worthy, and the exception was lost; it went back to its default state of being illegal.
This law could have amended the DMCA to permanently allow cellphone unlocking. Or it could've directed the Library of Congress to always find that cellphone unlocking is allowed. But it does neither of these.
Instead it only reinstates the rule from two sessions ago for the remainder of the current session. Next year it will have to be argued again, from scratch, to the Library of Congress, or lost, again. And even if argued, it can be rejected, again.
This is less than useless. It's only a temporary patch, it doesn't even have an iota of long term effect (the rules don't take precedent into account, and this doesn't change it), and we've wasted all this effort getting it instead of something worthwhile.